Hi ashim24810, welcome to the forums,
Sorry, but I don't quite know exactly what you're asking.
AFAIK most blogs use a limited set of bbcode that is converted into the rendered HTML
So it depends on what HTML you are wanting to include.
Are you talking about your own blog?
If so, you should be able to use bbcode tags.
Or are you wanting to show code snippets?
If so, you should be able to post code inside
If you are talking about other's blogs, they may or may not allow bbcode in comments, and they may or may not see it as an attempt to SPAM their blog.
Or are you asking if search engines will consider the comments as SPAM?