total nuking of thread? rare and maybe something only the top mods or admins could do and usually for high level reasons. usually, it's just threads being locked which then get quickly shuffled off the front page due to the quick movement of threads.
Edit the post into something forbidden and then hit the report button, I'm sure the mod will take care of it
start talking about anything, politics, religion, in another language and everything that is not allowed in the forums I think that will get your thread destroyed
You can't, you can ask a mod to lock it to prevent further discussions in it. It's for record purposes and some rights and all I guess... Remember reading about in some locked thread a long a while ago.
Fyi, we usually reject any request to delete a thread/account. The thread will only be locked. The only exception to this rules is if the thread is made by a spam bot.