If the person already has an account, you can add them to your blog.
For a full breakdown of the roles please see the Edublogs guidance on roles.
Log a request on IT Self Service Portal that includes a list of blog URLs that the user with a St George's legacy email address requires access to and indicate what role they should have on each of the blogs. The team will create a local account and add the user to the relevant blogs.
Your blog Dashboard also displays recent comments. If you are viewing your blog, you can see a count of the number of comments for each post and selecting on the number of comments opens these for you to read.