(possibly) unpopular opinion: if someone takes the time on tpf to offer a written (e.g. non-emoji) compliment about your picture/item, it is good form to acknowledge that, somehow, if even by an emoji.
There was a time on tpf when the emoji reaction option wasn't present. Yes, it added to much longer threads. Yes, it took more time to respond and sift. To me, that just makes actual narrative/written compliments all the more precious in the present day. Acknowledging the time/care/concern extended by a written compliment is a gracious gesture.