I think it doesn't matter, some people take lots of time to plan a well thought out and worded post and no one responds or likes it, and some people make 3 word messages in condescension of that same message and tons of people like it and respond to the troll comment.
Personally I would rather remove the short trolling messages because if I wanted to read trollish one-liners I would be an active member of FB or twitter.
In the end this is a preference thing and like I have always said, if you are not willing to help fix what you personally believe is a problem without adding a different problem than it doesn't matter...peter paul and robberies and all that.
An addon could potentially be made to check for line breaks and if none exist display a message stating "your post may be unreadable, consider using paragraphs"
The problem is technically three sentences is quite fine for a paragraph like above and really if it is one paragraph the breaks aren't even needed or appropriate.
Since not everyone thinks that way or alike in any event...
A text analysis system is possible but it is not a simple thing and it will add overhead and that type of thing is a system which is best suited for an API service and to be honest it would probably cost more a year in requests to use a decent service than a copy of XF+renewal. Anything simple and generic would interfere with normal acceptable posting activity probably pissing legit users off and thus it is not a reality unless you want to put up the coin for the development and what would most likely be a rate plan with an outside service.
In the end I still have only seen systems which return an analysis of the text and not any corrective replacements so the best you would be able to do is force feedback on posts to users when an unacceptable quality threshold has been passed, maybe like a notice that doesn't go away until they edit the post and make it nice, or just plain hide it from everyone other than the posting member...which will probably piss people off if not instantly then eventually.