You should upvote comments. It costs you nothing, and will gain you loads of fans, who come to your posts, if only for upvotes.

There is no bad publicity, and free publicity yet.

Plus, it's just how Steemit works. When you find a comment apropos, toss it an upvote, and help the ecosystem distribute Steem away from whales, into the wallets of the little people.

Thanks!