When someone is giving you advice on improving your art, handle it professionally and don't be defensive about it. As I learned, in order to improve on your art, you need to accept constructive criticism and not deflect it.
It just makes you look like a fool, somewhat.
Even though a person is bashing you, either you hide the comment or block the person that bashed you and stuff.
Like, if you reply back with an even worse comment, you're just adding fuel to the fire, inadvertently starting a comment war.
Then again, as ~WiseKarasu (https://www.deviantart.com/wisekarasu) pointed out in one of my older deviations:
Yep, even negative criticism is good if it makes a valid poin