Heh! That happens to me a lot, too. And talking about the good in the story and not mentioning the bad or working in some concrit (after carefully checking the author is ok with that) in a way that's not insulting the writer ist just 1. too much work, 2. above my skill level both wrt language and social skills.

It really amuses me that I mess up the hit count of stories I love (and where I commented!), too.