There is more on this on the SEO page of this blog, but here we want to talk about what commenting can do for branding purposes.
The same applies here as in commenting in social media groups. The biggest benefit of course is backlinks, but if you are commenting often, people will start to remember you.
Then, when they see you somewhere else, they will remember you from what they have seen. If your comments exhibit your expertise, even if it only in one area, that is what you will be remembered for.
This is yet another tool to help with your branding efforts.