The wording when you send a thanks message has changed. Instead of Yes or No it says Thank and Cancel. It is also now easier to understand that all thanks are public.
A notification is now sent to account owner on multiple unsuccessful login attempts.
Between week 7 and 20 February, when you thanked someone for an edit, the thank went to the latest unthanked edit to that page. It didn't matter which edit you tried to give thanks for. This has been fixed.
Long page titles on Special:Notifications were not truncated. This is now fixed.