As it should always be, I have read through the thread before even voting. Of course, I've had a sentiment against this ever since it was proposed years ago. The arguments in this thread have led me to go from "it'll be incredibly annoying" to "it'll probably only be another nuisance". However, the benefit to be gained from this is absolutely minimal.
/introduce is a two-way concept. Depending on implementation, one can introduce to a name, the target or everyone in range. Possibly to a guild, but the latter already makes for more or less the same as it's ATM, with guild members offline, etc..
So with this command every player would be forced to not only enter the command with the appropriate targetting first (I already find the /greet command annoying because I have to change the target, then click a shortcut or type a command; I occasionally use it, even though I find /me-ing more appropriate, especially since the (very nice) /greet animation hardly ever fits the situation (it appears to be extremely formal)), but to get everyone else to do the same (highly likely to lead to several lines of OOC chat, which would not have happened without /introduce).
The /introduce command will likely have no visual representation, so it's use will be even less appropriate, meaning less incentive to incorporate it into an RP session.
This leaves us with what it's trying to do: enforce proper RP on everybody. Now, the idea of having no OOC in /say had to be dropped already, because it's simply not possible to get people to only talk IC. /introduce creates the impression that it'd be possible to force people to RP properly. However, it isn't. The only thing it does is to hide information which is, as many of the replies already stated, vital, due to the (currently unsolvable) lack of absolutely unique looks. Even in a game like SL, where customisation is almost excessive, labels are needed, because not everybody will be able / capable / willing to ensure an individual look, nor is the visual resolution in PS (or anywhere else) remotely good enough to distinguish between people unless they're complete freaks.
Still, the problem is that people address characters by name without having being introduced or otherwise come to know the name. I can't help but consider this a ridiculously small issue. This sort of thing has happened to me, yes. However, it has never been a problem. Granted, my character has properties that lend themselves easily to a description and subsequent recognition (so that I could shrug it off IC-ly very well), but still I don't recall more than 4 occasions in my entire time in PS; given that I likely don't remember many of them due to their insignificance, I'd accept a factor of 10, making it fourty times, a number which is both extreme and low at the same time, given the ratio of occurances to playing time.
Then add to this that it's been common practice for non-secret guilds to have IC means of recognising the char's guilded status, be it a badge, a tattoo or something else. Of course, this is in response to the existance of the guild tags. However, given that guilds are popular exactly because of these tags, it's highly likely that people will wish to show off their guild token regardless of introduction. Only a fraction of that desire likely is IC.
This leads to the question of the improvement of the player's RP by lack of information. I am convinced that a player will have the exact same issues separating IC from OOC, or comprehending the concept of such separation at all, completely regardless of the knowledge of someone's name. In fact, since /introduce happens to be an OOC thing itself (being a command), and the subsequent display of the names being also an OOC thing, the idea of /introduce itself more likely serves to blur the distinction between IC and OOC, rather than to emphasize it.
Players not caring about RP will simply /introduce in order to get the names on the BL or whatnot, just like almost everybody has to adjust gamma to navigate the DR.
Point in case is, actually, the very incident ThomPhoenix cited: if the incident really happened like that, and if it was really justified to assume that the information from the boards was not likely to be known by that other player, it would mean that that player was completely unable to differentiate between IC and OOC. Let me just state that that player did, from ThomPhoenix's presentation, respond very well and completely appropriately to the clarification, and in addition that the place the information came from, be it this forum or any other, likely was classified as "IC area" on that forum; this means that it could just as well be concluded that not knowing that information would be OOC (especially if you consider the "IC area" of guild boards to be an actual visit of your character, with everything occuring while your character is there, which seems to be the very intention of these areas; forum-RP works in exactly that way, so it's only natural to assume that forum RP and ingame-RP are interchangeable.).
OK, assuming all of this was not the case, and the player really was unable to decide between IC and OOC... what RP, good or average, could ever come from this player? Is it not certain that that player will commit many other, much more severe, blunders in the ongoing RP, to which the name / guild issue compares as totally insignificant? I am convinced that this is exactly the case. The point is that a player who cannot RP will not RP. Even in the unlikely case you would manage to withhold all OOC information from that player, forever, the player would still not RP. Inappropriate acting, OOC remarks, all the true annoyances would remain.
Just yesterday, I happened to meet someone like this. The player was obviously familiar with the concept of brackets, since he began to use them after I had used parenthesis to respond to his undesignated OOC question. However, his usage was completely random, with things that could go for IC in brackets, while internet-related references in plain chat. He had used /greet, but he had not ever, in the entire conversation, addressed me by name. Therefore, even with the most restrictive and intelligent implementation of /introduce, the conversation would have happened exactly like it did.
IOW, the only way to force people to RP is to have the client do it for you. This would mean to either make it an interactive movie or to limit player interaction to choices from a list, just like it's done in SP RPG NPC interaction.
Thus, the gain is essentially zero, while the overhead is, while not necessarily large, but existing. Therefore, I can only say that it's not worth the effort, neither in code (which obviously has already been expended), nor on the side of the user who has to use the (already clumsy) interface.
My (much more effective) solution to this issue has been to simply not hang out in the notorious areas like Harnquists, the arena and the spawn points.
As a sidenote, I fail to see the reason for this sudden push for enforced RP, while, as stated, the char creation, by default, puts into the descriptions nothing but things that do not belong there. How is a player supposed to know that what the system does is against the rules? Are you seriously considering to punish players who take the time to write up something in their description, inspired by, or in many times coherent with what the system put there?
I'm baffled that on one hand you are willing to spend time coding enforcements, complete with all the forseeable (and subsequently all unforseeable) side-effects and inevitable corrections, while glaring issues like that remain unchanged for literally years.
/sidenote
I also considered the options to have a different label for unintroduced persons, and initially was drawn to one of them, but then I realised that the benefit of this is even smaller than with invisibility: the only people using it would be those who already are RPing properly, while the hassle would be the same (or even more, considering they'd not only need to get others to RP, but to use an obscure command in addition.).
@ Bilbous: I can't see the reasoning behind your explanation. The name tags are OOC. So unless your character tells it's name, it's perfectly anonymous (not unrecognisable, though), IC. OOC-ly, you want to be unrecognisable? Why? And if so, why do you state that your description has "his name and guild are tattooed on his forehead", meaning that it is, even for perfect RPers, impossible to not know your name? I'm sorry, but this makes little to no sense to me.
Consider me conservative, but if something is not going to bring significant benefit, while imposing recurring cost, then it's best not to do it.
Thus, I voted for "no change at all".