Technically yes it is a business mention, but I think you're actually asking whether this will help the business rank locally? It's most likely going to have a very minimal effect, if any. Google could use that to build trust in the NAP, but if you're only making comments like that to create citations then I think you're wasting effort.
I guess it depends what site you're leaving these comments on, and what type of comment it is. Comments are made to give a forum to discussion about the article/topic, so if leaving your NAP in there is helping the discussion - cool. Do that too much/don't contribute to the conversation well enough, and you could get your comments blocked by a moderator. You're better off using links in comments to relevant posts to help grow the conversation.
Yes it's called an unstructured citation. If it's on a blog whose comment links are no-follow then it won't provide the SEO juice you are looking for, but it can help NAP a little. Make sure it's on a same niche site if you are going to do this.
Assuming your comment doesn't get deleted, try to make it look nice, add value, answer questions. If I leave a link, I am usually the longest poster in their comments or have a couple of paragraphs built in, with a question back to the Author so he gets some participation from me.
NEVER stick to just one method of gathering NAP or backlinks. I am a huge fan of using blog comments for traffic and getting on influencers' good sides before I pitch them for guest blogging, or to index certain properties.
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