Totally agree with you! I mean, I don't want to sound like a snob but it really bugs me when people leave generic comments on layouts, and for that matter, BLOGS! "Nice blog, follow me" um what?
It's not hard to actually LOOK at the page and point out exactly what you love about the layout you're commenting on... Even if you don't think "Wow, I wanna add that to my faves", there's bound to be something you can compliment! I know I always make the effort to leave comments like those, and return the favour to those that do the same
