In the same line of thought as Tom J, Ian M, Kravenwolf, and a few others who have already posted, it does seem like there are definitely different ways to perceive this situation.
For example, I use RSS feeds to check on what's going on in the forum. If I didn't, I wouldn't be able to keep up. If I see something of interest, I make a note to myself to look at it in more detail later. So, even after viewing your post, I didn't download the song yet and therefore had no comment to make. I want to give something the time it deserves before analyzing it or saying something carelessly, especially since I compose music myself! I bet tons of people on here use RSS feeds; one of the greatest things since the start of the internet. Many of them probably look in at everything but don't necessarily get involved because it may not be of interest to them after a quick look.
I am sure there are also people who lack social skill, some of which are probably people who don't even weigh the pros and cons of commenting on someone's free items because it simply doesn't occur to them; I've been a dumb person in the past who has done something completely and socially unacceptable but didn't know it until I got verbally ganked afterward. But, there are also people who would have taken the time to comment, thank, and so forth if they had the time to. I mean, I haven't been here that long, but I can already tell that the regulars here seem to be nice enough, even when somewhat unfiltered with their frustrations.
The point is that there's going to be some of all kinds of people and it's impossible to stop people being how they are. Having been in similar shoes to yours at a point many years before, Armaggedon, I think the question isn't necessarily how to fix the problem with other people but to ask yourself if it's worth the stress of giving away items for free. If it makes you feel used, maybe you should charge for it, even if it's a very small amount. I mean, even if you force people to comment, the comments may not live up to your expectations or hopes either and you could walk away still feeling used. I can already see in my mind's eye people making a short a comment as possible just to download faster. :}
Edit: An additional thought... If it's music, what would people have to say about the song other than thanks before downloading it? :}
Your error is my treasure. =^--^=
