I got the commenting fixed on the blog!
In the upgrade process, I forgot to readd the .htaccess file which ensured that the permalinks work properly.
Couldn’t understand why I got so many 404 errors on the blog until I realized the step I missed.
Have added the necessary .htaccess file in the directory and everything works fine now.
Those who wished to comment (I’m sure there would be someone ;)) on my posts, you may do so now.