Technically blog commenting does not have any SEO value as most of the blog owners provide nofollow links to their comment section. But It will definitely count as a backlink. Practically, it won’t pass the link juice but it is a great source of building backlinks.
Blog commenting does not mean that you start spamming the blogs with keywords and links. This is a bad practice and believes me your comments will be trashed by the bloggers and also it will put in the spam section.
Always write in-depth and genuine comments that have added something extra to the content. It always adds something extra to the content which helps the readers and starts an engaging conversation.