This was in-game not long ago, but removed due to some problems.
I'd rather not go into that discussion again, but the feature it provided was very interesting and I feel it would deserve a resurrection.
Why?
It would help with immersiveness as well as improve the way we "speak" to the NPC's. Basically, it feels more natural.
How?
* "Hello NPC_name" (full or short) triggers discussion with an NPC if in his/her range. Does not necessarily require facing the NPC. Does not get triggered when using the name of the NPC out of context.
* "/greet [NPC]" also triggers a discussion
* "Goodbye NPC_name" (full or short) triggers the end of the dialogue. It can also end if the discussion has been idle for more than a reasonable time (1, 2 minutes?). End of discussion can also be triggered by shift of focus from the chat tab of course, just as it happens now.
* The old way of talking to an NPC, via the select & talk way should still be valid as an alternative.