All The Tropes:Repair, Don't Respond
An in-wiki admonition that speaks against explaining why an entry is wrong or incomplete instead of just fixing it.
A common offender is the Justifying Edit ("Well to be fair, the show was right to use that Trope because..."), but there's plenty of variety, from "Not to mention that..." tangents through "However" clauses which make the page seem like it's arguing with itself all the way to paragraphs on end of aimless chatter.
The second/third bullet point is oft-misused to reply to an example; sentences that obviously got tacked onto a paragraph as a response are also commonplace and may be even more disruptive. The tone may be polite, passive-aggressive or sarcastic, but the result is the same: Concise examples turn into walls of text, the wiki loses its consistent voice and the interesting parts get drowned out in all the noise.
Why do these pop up? Perhaps the troper who wrote the entry was being overly polite and didn't want to hurt the feelings of whatever troper wrote the original article by deleting their example and writing in the corrected version instead. Or they wanted to show up the previous troper, keeping the incorrect version alongside the "correct" version. Or maybe they were under the mistaken impression that main article space doubles as a forum, a blog or a soapbox, and that we encourage that sort of thing.
If it's to correct a misconception or to add more information, it can be integrated into the existing entry. If a response can be reasonably removed, it should.
Related, if you are going to remove something, make sure that what's left behind still makes sense. Conversation in the Main Page and Sinkholes are bad, but a bullet point directly referencing something that's no longer there isn't much better.
No one is going to complain about the vast majority of the changes you want to make to a page. Don't feel any compunctions about adding or deleting entries if you think that your impressions are accurate or defendable. That said, don't let your bias get the better of you and completely wipe out whatever you disagree with. If there's more than one way to look at things, they should all get their say.
The redirect to this page, You Could Always Edit It Yourself, is generally used in somewhat different circumstances, when someone complains that an example is wrong, or that a page is infested with Natter, or that examples aren't sorted, or any similar problem exists but they show no indication that they're willing to fix it or clean it up themselves. The message is the same, though -- if something is wrong, fix it.