to reduce the noise level? For example I created a topic this afternoon that is irrelevant at best, misleading at worst and solves no problems for anyone. It would be best if it never got into the Google cache. But, failing that, can 

You are able to delete until there are no replies AFAIK. In other (rare) cases just approach to one of the staff and it will be done.

IMO instead of deleting it's better to post a correction or clarification, or in the worst case edit your own message striking out the incorrect information like this.