Some users on my site have left comments quite a long time ago and then the account, through non use, has been deleted.

The problem is that this causes an error where the comment is supposed to show such as:

Creating default object from empty value in <removed address>/public_html/modules/mod_k2_tools/helper.php on line 125

Nothing I have found can fix this and that error is on the comments page all the time.

How do I fix this please?

You can disable error reporting from your site's global configuration menu.

Finally you either need to remove this comment or edit it and assign it to another user.

Thanks for the reply. I found that the article to which the user had commented was still there though the original poster of the article was deleted as well. This made all a bit difficult but I assigned the article to myself which cleared some errors up then as you said, I deleted the comments and that cleared the rest.

I hope that helps anyone with similar problems.

Thanks for sharing the solution :)