... when you send a friend invite or group application, you get an opportunity to write a message saying why you want to be friends/join the group. Trouble is, I've been on the receiving end of a few of those, and I have never had a chance to see what they wrote, not even the default message. Is this a glitch, or am I missing something?

N.B. it works fine for Tournament/group invitations, just not applications, possibly b/c you get a message for invites, while applications work differently.

Yes, Happened to me too, But I didn't submit it in the forum because I thought it wasn't something that really mattered to me :)

Yes, It's hardly a high priority problem, and I'd say that it'd be too much hard work for them to fix properly - they may aswell just get rid of the message boxes.

Do people actually use the message things, btw?

I don't  :)