Well, while I'm not quite a fan of linking EVElopedia articles in IC discussionas/debates, I have to admit to making relatively ample usage of it n IGS.
The reason why I don't like it is that it's very aggressively hammering a point across. That is the case regardless of whether one perceives the EVElopedia to be an IC tool or not. Why am I still using it on certain occasions? Because sometimes, the only proper response for my character would be to write just said article in response. Besides the C/P being kind'a senseless in that case, imho, I oftentimes took the time to retell the stuff with my own words, writing a good side or so why x != y. What happens then is one of three things:
a) The ignorant char opens up for real debate about it. (Which is fine and most fun to me.)
b) The ignorant char makes clear that 'facts won't confuse him'. (Which is also fine by me and something I do myself with Nico, sometimes.)
or
c) The ignorant char goes off on a 'you are wrong and you can't prove me to be wrong anyways'.
I think the latter is being a problem, here. There have been cases in which I was then pulling up news reports, done my utmost to produce evidence and such to make my point. The problem is, our Chars in EVE have only that many sources at their disposal. I can't get over to the virtual shelf and produce the parts of the Scripture that produce, e.g. the parts that point out that the Emperor doesn't have the privilege to alter Scripture permanently and that this power rests exclusively with the TC. At some point in a discussion like that, you have to get out the battering ram.
Honestly, there came a point when I gave up playing nice, because it's a giant load of effort. It's easier and also not inappropriate, I think, to write a short response detailing it and to include an EVElopedia link to the relevant page. I'm not really of the conviction that one should stand back here for courtesies sake and do a private EVE-mail. If characters blurt out their ignorance in IGS, then they have to be prepared to be battered down.
Sure, though, there is another problem with linking EVElopedia articles. It's whether they constitute an IC source or not. Well, I think it should be clear that only EVElopedia articles that are CCP approved do give reliable PF info. The thing is that CCP doesn't make it easy for us RPers and has a wild mix of OOC and IC infos in their articles. I think the IC/OOC tags they have could be used much more efficently there. A good example of this is, imho, the article on Jamyl Sarum.
Here, the rule of thumb that Nmaro offers isn't a bad one.
In the game itself, I tend to not use the EVElopedia and if I do, I post it occly to the person in question, either in an ooc channel we both are in or by evemail.