Threads are deleted if they are completely useless... In this one you requested for help and it will probably be closed. And only moderators can close threads. I for one am a moderator, but only in the spells section. Conclusion? I can only close and threads there.
And polls are those stuff where you vote for something. When you post a new thread you can look at the bottom for polls option. This is all the information I can give you.
