First of all, thank you, Smart, for this wonderful extension - this is exactly what i have been looking for! I am going to vote for this on the Joomla! Extensions Directory page.
Also, thanks for providing the solution to this issue. I implemented the solution in a slightly different manner, as follows:
Instead of inserting the text directly into the
jcomments.ajax.php file, i created a new text entry in the
/language/en-GB/en-GB.com_jcomments.ini file (people should use their own default language file), as follows:
ERROR_EMAIL_EXISTS=This email is used by a registered user. Please login or use email.And then i change the code in
jcomments.ajax.php as follows:
from:JCommentsAJAX::showErrorMessage(JText::_('ERROR_NAME_EXISTS'), 'email');to:JCommentsAJAX::showErrorMessage(JText::_('ERROR_EMAIL_EXISTS'), 'email');This solution is working as expected, and i think is a slightly more "canonical" approach, which i am sharing here - hopefully people will find it useful, and maybe you will include it in your next release

Once again, thank you for a wonderful extension!