A user on phab.wmflabs.org has been closing tasks on some of our mockups. I thought maybe this was an honest mistake (it's a test env, so it's easy to assume it's just a place to mess around with whatever), so I reached out to them to ask them to stop and why and offered to help them with whatever they wanted to do. I also added a description to the project in question. After reverting their changes, however, they did it again. I've noticed this user is blocked on some wikis and has a disabled account on WMF production Phab, so I suspect their intent is simply malicious.
At the end of the day, I just want my mockups to be preserved (we're doing it in a test env to not overwhelm production). I think my best option is just to manually change access for each task. Is that accurate?