I made a testing thread with some posts in Archival, but I can't delete my posts from the thread. I have to move it to Off-topic only to delete the posts and them move it back to Archival if I want to keep it for testing?
What is the reason to have the posts locked for deleting in there?
IMO Archival is the place where mods would move something they would otherwise delete but decide to keep for posterity, as thread may contain relevant info (ie service complaints, project accusations etc that might be worth "archiving"). Thus disabling the option to delete post from the threads moved here sounds like a good decision to me.
It allows Jr Member and above users to open threads (not sure, might be wrong regarding the rank ) and also use it as some sort of testing ground.
Personally I would make it read-only tbh and advise users to post testing threads somewhere else on a new child board in off-topic ... dunno
What is the best place for a testing ground threads?
For the moment that is the place, but not designed for that so has it's pluses and minuses.