How many comment? You can comment as much as you like on someone else's blog, it's down to them whether your comments are seen as relevant or spam. And your own posts can theoretically have near enough unlimited comments from other people.
As CM30 Said; You can comment as many times as you like on someone else's blog, but you will most likely get allot of spammers. I advise if it's your blog you make it compulsory for their posts to be put up for moderation first if possible, then you can approve the posts if they're worthy! 🙂
