As a low-reputation user whose interest in Japanese is more of a hobby than anything else, I'd like to add my support to this idea.
When I first joined JL&U, my intention was to only ask questions, and never to try answering; I didn't want to accidentally spread misinformation due to my comparatively low skill level, especially when we are fortunate enough to have actual, native speakers whose knowledge is incomparably more useful.
However, I have tried to provide answers to one or two questions where I was reasonably certain that I could provide a correct reply. Some of these answers received helpful comments, such as this:
It's probably worth slightly editing this answer to make it clear to OP it's relation to ゆっくりする specifically – sqrtbottle
「サッポロ」, along with so many place names in Hokkaido, comes from Ainu, not Japanese. We can't let the kanji fool us. – l'électeur
I'm certainly not upset by this kind of feedback - I am aware of my own limitations, and I really do appreciate constructive criticism from anyone whose grasp of the language is better than my own.
tl;dr: Adding comments to answers provided by low-reputation users doesn't just warn those viewing the answer about any mistakes - it also helps the user providing the answer, by letting them know which parts of their understanding are (in)correct.