Originally posted by MissOleum
With respect, if he's rated below 1500 he's not using an engine - trust me.
If you'd catch someone like User 168990
at the beginning of the ascent, you'd get exactly what LLW51276 describes. However, there are several other possible reasons. For example, the player could have played carelessly at the beginning of the game and then started to think more about the moves and maybe use the analyse board. Or xe just got lucky with some moves. Or the moves were not actually very good, but looked very good to LLW51276 - I doubt a 1100 really can tell the difference between mediocre and Kasparov-like play all the time (actually I don't think I
always can, and my rating is around 1700).
Anyway, if you have good reason to suspect engine move, send feedback (link at the bottom of the page), giving as much information as possible (tell them which game / moves made you suspicious and why).