Reported today by an active ukwiki user, that got autoblocked after a registered vandal block. See Autoblock list on enwiki (several hundred users got autoblocked without an option to see who exactly got affected by it), and on ukwiki.
Fix it asap, please.
I have closed this task, since it seems to be an intended behavior, per this enwiki page. Still doesn't make much sense to me, since when you block a separate IP address, you don't have to prevent the registered users from editing (even though there's an option for it). I don't get why autoblock does work that way.