Many people suggest and do follow the strategy of commenting on related niche blogs with links to their own sites. Is this legitimate and a good way for SEO? Or it has some harmful side as well?
It's not just the back links, it's the reputation. You should become a member of relevant website communities. You should be helpful and friendly. You should recommend your website when it is appropriate.
- Don't hide your affiliation.
- Use your real name, or at least a consistent nickname across different sites.
- Limit your membership to ONLY relevant sites.
- Post only when you have something useful to say.
- Don't recommend your site in every post you make. Try for 10-20 %.
- It doesn't matter if a site uses nofollow or not, post anyway.
- You can't always link, in such cases a domain name mention works just as well.
Get a backlink through blog commenting is not bad. But you should be putting a backlink on the related blogs only.
For eg if you have a travel site and you are commenting on a tech blog and getting a backlink from there, then it is a serious issue. As per the recent Penguin and Panda update, if any site is giving link to any other site which is no where related to each other in terms of content. Then both the sites will be penalized. Google consider it as paid link.
If you are posting good content (such as good thoughts, ideas and constructive criticism) there's nothing to be afraid of.
Maybe you need to look at this argument from another point of view. Don't expect to see your analytics to grow after every comment. Simply comment because you like it. Tell the other everything you know and that could be useful. Be generous.