In my own experiences, any backlinks would help yours SERP in some extents, if only they are from decent sources. Of course, no follow backlinks would not benefit your PR. all the best,
Dont be confused between No Follow and Do Follow blogs, this is only for search engines and your ranking will not get effected by this.
Nope, they will NOT harm your SEO. They can help you to gain traffic because if the users sees the links (for example in your signature) and it is appealing to him he will click it. They are not so helpful as doFollow links but they can help you to gain traffic.
I would be happy to have 10,000 nofollow links to my website. No doubt some of those links would bring some traffic.
Obviously, it won't be harmful to your site. On the contrary, I think this kind of link is useful to improve your quality of your site although it can't pass the link juice indeed.
Nofollow links can be good for SEO etc if you get a whole bunch of them, but theyre nowhere near as effective as dofollows.