User blog comment:Rappy 4187/Technical Update: February 17, 2015/@comment-126761-20150220144620

If you see some read-only periods this week, it's because we're flipping some switches on a few servers. We're trying to make it as low impact and quick as possible (~30mins or less each time, on a subset of communities). Please do feel free to ping us if you come across issues - there's always a chance it wasn't supposed to happen that time.

And a bonus note: some users spotted issues when trying to edit via the mobile skin since this week's release; a fix for this issue was pushed live late last night.