I did once from my @requiemforadawg account as a joke and immediately regretted it. I would definitely never do it from my personal account. It is creepy as hell for me to see some 45 year old dude with two elementary aged daughters in his avi groveling over a 17 year old kid.
A lot of people from sports message boards do. I do for anonymity purposes.
I follow a few and retweet or "favorite" a tweet if its positive message about MSU. I will never tweet at a recruit though. That's where I draw the line.
I will contend that retweeting a recruit's message is no different than cheering for him a high school football game. It's just a way to show appreciation of what they are saying or doing. I don't see anything wrong with that. If you do, you are probably over-thinking the whole the deal.
If I'm obtuse, then explain to me why you need a twitter handle for you sports message board persona and your personal life? When do you need to tweet as Requiem for a Dawg and not yourself?