I'm sorry if I was a bit crude
But lists which 'teach' the wrong thing only encourage people to use the 'wrong' abbrevations even more. Aka: you do the opposite to what you meant to do. Those who don't know 'MSN' doesn't stand for 'Messenger' (which are a lot of people as you know) will not be teached the proper thing and they would keep on thinking it is 'Messenger' because it is listed like that in lists like this.
As for not so common abbrevations (like 'DP'), as I said in the previous post, end your post with a small line explaining what the abbrevation means, easy as that...
A list of these would be nice. But there aren't that many Messenger related and thus a list isn't really needed I think (most are simply made up and only used by one or two individuals anyways). And those which are listed need to be correct (eg: 'IM' is not 'conversation window').
In general, I strongly believe that on forums as this, abbrevations should only be used when they can't be misinterpreted, with the right meaning and when it is very clear what people mean and that they understand it. Of course people are free to do what they want and use what they want, but it makes things harder instead of easier.
As far as support goes (and asking for support too!!!), the use of abbrevations like the ones listed can cause a lot of misconceptions, wrong assumptions, unclear information, etc. And thus shouldn't be encouraged. This is different for abbrevations like 'imho' etc though ,which are very common and only have 1 meaning.
For example, when I talk about different versions of Messenger in a post I would never use 'WLM', 'WM', etc (and certainly never 'MSN') but the full proper names.
Or when you're talking about Windows Live Mail and Windows Live Messenger in one thread, you should never use 'WLM' as 'WLM' is also sometimes used to indicate Windows Live Mail. etc...
So, the idea is nice

... but should be made carefully and correctly. And instead of helping people it can do the opposite and encourage people to use abbrevations, which is not good (at least not on support forums), imho.
Hoping this was explained a bit more friendly 