You're kinder than I am, voting up a comment when you know they've not read the post. I often leave a reply like, "it's clear you have not read my post and I'd appreciate it if you would either read my post prior to commenting or just don't comment at all."
Sometik snil also ask a question back to them about my post and in those cases...usually get no response back. Says it all really.
As for your last...not commenting often. I look for accounts that comment on others (I mean newer accounts) and with some personality and effort and then try to support them. Of course, if they post in languages that are not English I never read them, I don't use translators, so those people miss out.