The addition of such command, as ralas said already could serve to add colour to the ooc sentence.
But while that can seem nice at a first sight, I don\'t see if it really would meet its objective. That is, ooc chat and ic chat are in the same tab (no doubt on that) when someone types your name, the sentence is coloured in a way that is easily spotted by you, the reader.
Consider that, with colouring, the ooc sentences would become more noticeable to your eyes, than the real ic ones (which are the important) you can say, well, I can edit the colour to another one, more neutral. That\'s correct, but lots of colours that could be chosen, don\'t go well with the default background (such as blue one, iirc) so that will lead to an almost unreadable ooc sentence (and some ooc sentences are worth being read, either way we could be missing important comments, or clarifications about the outgoing action, of the attitude of a certain char, for instance) that will lead to choose, I think, a colour such as grey, which could end so similar to the default colour one that it looses its purpose.
I personally think that, if someone doesn\'t type a \"(\" or \"[\" at the beginning of his/her sentence, it\'s even more unlickely that he/she will type /ooc (yes, there are more letters ;) ) while this last option would ensure that the resulted sentence has both \"(\" and \")\" for a \"visual filtering\" of ooc sentences, really the only parenthesis needed is the first one (which almost nobody forgets about)
EDIT: Smiles on were playing with some signs used. :P