We don't have an official rule. Rather than post "Do a search, noob!" I try to gently persuade folks to post in the existing thread like the example quoted. If the conversation continues in the new thread, and I notice it, I'll usually merge them. Sometimes it doesn't make sense to merge, as discussions head in different directions, so with the OP's permission, I'll rename the thread to better describe the conversation. Sometimes they just go unnoticed.
I'll be the first to admit that the search here is not always helpful. It won't even bother to search 3-letter words unless you put in a user's name to reach by. So unless I remember posting in a thread on MPG, it doesn't show in the search results.
Search also defaults to only searching in the current sub-forum.
@Michael might want to change that setting.
If anyone sees threads that should be merged, tag me or any of the moderators and let us know.
Thanks,
Steve
(merging these threads now.)