I find commenting time consuming and mentally and emotionally taxing. I often read a fic I like and don't comment, because I just don't want to engage. I read fic to relax, and continue on to the next fic after reading the previous fic to relax some more.

So yes :-)

But I might start commenting with something short and sweet when I read a fic I suspect I'd like to reread sometime, or would want to be able to find again using gmail's internal search function, if I'm in the mood for more by that author and I don't remember their name (which often happens).