No idea of identifies but the amount of times there have been decent buys at 17 or 17.5 before a 2m and a 900k sell order pops on at 18 and 19.5 has been uncanny.
I have seen that happen at least a dozen times. The orders then disappear overnight or sometimes when only a half an hour or a few hours have expired.
Also saw what you have mentioned, which was also quite unusual.