Was wontfix upstream: https://secure.phabricator.com/T6905 -- we must either Decline this task or discuss a local change. But see also https://secure.phabricator.com/T10343
When I close an unassigned task as "Resolved" in the Comment action, Phabricator automatically assigns the task to me. This is often what I want, but not always. It shouldn't happen automatically - or at least there should be a way to opt out on a case-by-case basis.
See T75462#852055 for an example. I closed the task because it became obvious to me that it had been resolved, but I didn't actually have anything to do with the resolution itself!
What is worse, the preview area underneath the comment box doesn't warn me that I am about to claim the task. It just shows the "TTO closed the task as Resolved" line, and any comment I may have typed.
A solution is to edit the task, mark the task as resolved and assign it to a user other than yourself.