This is one of the sufficient step to switch to wordpress etc platforms where universal gravatar look is prevailed which is not so in case of blogger .
This is the main reason people switch to wordpress or go on finding wordpress comment form kinda alternatives that makes readers to stop and comment !
There are only two good alternatives as per as i know, Go get em !
- Intensedebate - very famous are similar replica of wordpress
- Disqus - yet another similar intensedebate but not too much preferred
Will again write on these two plugins till then , enjoy commenting on new comment form instead of default boring blogspot one :D