Also please use this CSS code to fix the top-jumped avatar issue:

.author-avatar {position:inherit!important;}

Posted by: Robert

 

Please navigate in Dashboard to Forums > Settings > Styles admin page. Put this CSS code in Custom CSS Code textarea, save it , delete all caches and do Ctrl+F5 on front-end. Then refresh twice on your Tab.

I've tried doing this but it doesn't seem to make any difference.
Is there any documentation anywhere explaining what this code is designed to do?

I don't see the code I've asked to add in your site. You did something wrong or didn't delete all caches. Try  to put both code in current active theme styles.css

Posted by: Robert

 

I don't see the code I've asked to add in your site. You did something wrong or didn't delete all caches. Try  to put both code in current active theme styles.css

   

That is certainly possible - I don't know how to clear server-side caches on the website (hosted on tsohosts)

I have tried adding the size code (not the avatar code) to the live site but that doesn't seem to make a difference either.

Really appreciate your support - any further pointers appreciated.

But I asked to put it in active theme styles.css file, save it, then delete all caches.

I have no clue then. You should reinstall your WP on other hosting services. Or maybe you're doing all wrong.