So... you might know this game: freeze a mob with a bomb, walk around it, lay another freeze bomb directly behind it, step back so it doesn't hit you when it gets damage by the bomb. Mob now looks the other direction, walk around it again / repeat.
Well, it doesn't work with players. They hit me, when I am (1) clearly out of reach and (2) not in the direction they are facing at a time they are (3) frozen.
Don't think this can be explained with lag / latency, so that's a bug? It looks to me, like they take a step that they shouldn't be able to make and even though the game corrects their position (doesn't let them actually move), it registers the hit (that would have succeeded if the "client" would have been right about the player moving). Especially visible with flourishes - maybe there's something wrong with the order in which those "high priority damage events" I heard of come in and the sanity check on player position? Dunno, you figure it out! :P :D
The flourish and snarby swords have a really massive sweep on their first hit. If you mix that with a bit of lag (what, lag? in spiral knights?), it'll look like they're hitting you from the wrong side.