Funny thing is, there isn't. People manage to comment anyway. You're not supposed to jump into the main pages of tropes sharing anecdotes or whatever, and if you want to correct something, you go in and edit it; no matter how much the site tells people not to, most tropers will just attach some "well, actually..." comment onto the offending sentence.
Also, when giving an example of a trope, tropers have a habit of placing the example with some smarmy comment about how the example should have been on here already, i.e., "Come on, people, <some show nobody has heard of> isn't on here yet? FOR SHAME"
Also, people regularly use hyperlinks to compare themselves to positive tropes (like "Lazy but Brilliant") and, if they're arguing with someone, their opponents to negative tropes ("You Fail Logic Forever").
Those might seem like nitpicks, but given how much the site tries to stop people doing things like that and how irritating it gets after a while, I can't take it. That's why I'm not a big fan of the place.
It's a wiki, yo. Fix that shit! You'll do the world a favor.

(In their defense, it's only recently that the site has started to crack down on bad writing, and it's gonna take a while to edit out all the outstanding problems. IMHO, there's already been improvement.