The problem is that this is, yet again, being framed in the most unproductive way possible, by those who have little to no knowledge on the way these editors think and the way these articles tend to work. If you did, you'd realise that the problem with so-called "in-universe" information is not the information itself, but the tone. You wouldn't bat an eye if it was written from the proper persepctive ... but instead of attempting to spearhead a campaign of rewriting articles, which would be rather simple with a little research and a little work, the goal is to get rid of them and start anew.
The point of Wikia (and I speak as a bureaucrat on one and the founder of another, both based on a fictional universe) is less to give an "in-universe" tone (not all "fans" are droolingly obsessed with fictional details, despite the way you want to frame the issue) than it is to give them an outlet for /detail/ not appropriate for a general encyclopedia. Granted, the tone may vary amongst articles (Memory-Alpha has templates for this), but it's not the main focus.
In essence, I suppose the point is that, yes, articles on fictional characters and the like need to have analysis and context, etc. but that without "in-universe" information, that analysis and context is meaningless and valueless.
~~ Sean