I up vote a lot of comments on mine as well. Yet I talk a lot, so if I up voted all the dialog I have I'd have an extremely low voter % and power and not be able to up vote blog posts effectively. So people commenting and simply saying "Nice post" or something simple I don't always up vote unless I haven't been doing a lot of voting that day then I will up vote even those. I do at least try to remember to respond and say thanks. Though sometimes I forget.