I decided to try out a new comment system because, honestly, blogger's comment system sucks. I first tried to use intense debate, but that didn't go so well. I couldn't find any way to import the old comments, even though it is supposed to be possible. The FAQ says to go to "blog tools" to do it. There is no "blog tools" that I could find. I did find "tools" but there was no option for importing comments, only reinstalling, unistalling, and exporting comments.
Not to mention that, even if I tried to add the intense debate system to only new posts, it was added to all posts, which hid all the comments that I couldn't import.
I gave intense debate about 30 minutes. That was enough.
So, we'll see how disqus works.
It doesn't seem that people can log in with their blogger account, though.