First, I'm seeing some references to the old site location, which is http://sharepointcandothat.com/blog, but the /blog should not be there.
I checked your Jetpack settings, and couldn't find any references to your old site URL. If you still find references to /blog/, could you tell me where?
when users submit a comment, it's redirecting to the following URL, which is giving a 404 error...
If that solves the issue, you will need to contact the theme author to let them know about this issue.