Comments like the following. "Nice art! It reminds me of Naoko Takeuchi's work."
I find comments like this to be amazingly presumptuous. Not only is the commenter assuming the artist knows who the hell they've talking about, but it also keyholes the artist's work.
Also, you, the commenter, run the risk of offending the artist. Just because you like someone's work, doesn't mean the artist does. Many fantasy artists hate Amy Brown for example, because she allegedly copies Brian Froud's works.
I discovered I dis-appriciated these sorts of comments when someone called A Girl Called Kermit A "manga" with a cute "chibi" character. I shit you not. Does she look anime-esque to you?!
"Wooow..You draw just like Jhonen Vasquez." That's nice. So does half the intra-web-net. Thank you for shoving me into a category.
I believe that the only time comments like this are acceptable is when the artist themselves say "I was emulating So-and-So's style. How'd I do?".
I tried to rant like Anne Rice. How'd I Do?