I think that's possible in Phabricator's workboards, too? I can set a workboard to be sorted by priority, but then I can still drag tasks around to change their order within the column. (But if I drag a High priority task to below a Normal priority task, Phabricator automatically changes it to Normal priority.)

I didn't see this bug report earlier and was about to...start sprinkling error_log() everywhere to see what was going wrong. (What better way to spend Friday afternoon, right?)

I think so. I've tried it out on two dummy repo histories so far, and the outcomes are both good. My real repo is backed up, so I'll try it next.

For what it's worth, I can only recreate this issue if I use Spaces (which T8798 already mentioned). I'm on the latest stable (rP535c1a5f255e0da69ea5fbfb230b699eb5a152b1) with a dummy git repo set to project member visibility, and I tried cloning the dummy repo under the following conditions:

Hmm... Do https://secure.phabricator.com/chatlog/channel/6/?at=152610 and the "Original Problem" in the description of T6860 apply here as well?