i dont know but i think that backlinks from everywhere help in SERP if they are dofollow and not from banned/bad neighbourhoods...
People automatically assume blogger links are more valuable than others simply because google owns blogger but i am yet to be convinced that this is the case although that said those links will not do any harm at all.
To improve even more, you could consider blogging somewhere other than blogspot as well to get some variations in your backlinks. There are a ton of different free blog services around.
Robert, as I understand this, the subject is links from blogspot blog posts and blogrolls, not comments.