Conversation in the Main Page
On the Internet, you can identify a geek in the throes of an accuracy attack by his signature cry of, 'Um, actually?'. The 'Um' is usually added (and yes, written in) in a feeble attempt to not make it appear that the geek is being condescending, when 99% of the time that is exactly what he's doing. Another phrase you're likely to hear is, 'you forgot', the point of which is the unstated, 'but I didn't!'
Our articles and example lists are not a chatroom, forum, or your blog.
You're in the middle of reading an interesting article. But what's this? Something's wrong with one of the examples! Either it's incorrect in some factual particular, or there's something the original writer obviously didn't consider, or perhaps it's just not a good idea to have it on the page at all. So you click the edit button, and write underneath, "Actually, the way it should be is..."
Wait a minute. If there's a change to be made, you should be making a change. And if there's discussion to be done... shouldn't that go on the discussion page? This is especially bad to do in a "This X has examples of:" list, as it ruins the readability of the list. If not kept in check, this can lead to entries becoming more like forum threads. And if that's the case, shouldn't you Take It to the Forums instead?
This kind of thing is also informally referred to as "Natter". Mind you, this is okay in areas and namespaces that are made for it, like Wild Mass Guessing and Headscratchers. And a small amount can be tolerated in main pages, but eventually we like to see the conversations fade away and then get edited into more standard entry text. However, we're not nearly as anal as TV Tropes is about it, and we're cool with a bit of chatter here and there regardless of the location.
See About Rhetorical Questions for info on one of the causes of conversation in the main page. Another frequent cause is the use of YMMV items—this is one of the big reasons why we keep them separated on the YMMV pages.
A strong sign that you're indulging in Natter would be if your edits contain Word Cruft ("actually", "what really happened was"), or anything involving "I" or "This Troper". Another sign is that you're adding a third-level (or deeper) bullet to an existing example. See also Signal to Noise Train Wreck.
If you come across natter, either move it to the discussion page or just delete it. Your help cleaning up the mess will be appreciated.