Question brings back memories. I was an admin on a guitar forum (stratman50th- get the connection?) The webmaster/owner/admin had God's rights and could do everything. They assigned rights to the lesser admins and mods. Deleting entire threads throws things off just like in any database. Deleting is a very last resort. The best is to just lock it. The thread still exists for searches and statistics but dutifully marches down the page to die it's inglorious demise. So in other words no, you don't delete threads, even as an admin.