actually you are incorrect l extensively use vbulletin for my own forums
the options to allow for editing own posts are contained in the adminCP under Usergroups > Usergroup Manager, within the page that loads up there is a set of options under the "Post / Thread Permissions" with yes/no radio buttons one of which is "Can Edit Own Posts" the other "Can Delete Own Posts" while below that is "Can Delete Own Threads" which you may want to keep disabled, in the Vbulletin options under "Message Posting and Editing Options" sub option "Time Limit on Editing of Posts" can be set up so that the post can be indefinitely edited so information can be updated if needed which will stop double posts, which lve seen mods warn against hence my point of not wanting to be given warnings because l couldnt update information.. however if as you say you dont want members to delete or remove their posts if they feel they have posted in the wrong thread or upon second thought found the information incorrect, whats the point for posting in the first place... and been able to fix my own double posts when accidentally done will cause less work for the mods...
on a side note please dont take offence to my reply, l just feel that some of the setup has us members on a tight leash especially on post editing which lve never seen a forum not allow anywhere else, just seems way too harsh.