Hi everyone!

I'm also about to add jcomments to my multilingual website. But I've ran into the exact same problem.
As you can see in the first screenshot below, the special characters are correctly displayed in the comment title and body, but they are messed up in mouseover descriptions and other jcomment elements.
I've tried your above solution, but it didn't work for me - I've probably done it wrong somehow or overlooked a table.
I logged into phpmyadmin (didn't have to do something manually in there for ages) and for the following tables I used your query:
jos_jcomments
jos_jcomments_custom_bbcodes
jos_jcomments_reports
jos_jcomments_settings
jos_jcomments_subscriptions
jos_jcomments_version
jos_jcomments_votes
If I understood correctly I simply had to copy your below SQL-command and replace the "table" part with "jos_jcomments_reports" etc. for each table.
ALTER TABLE table CONVERT TO CHARACTER SET utf8 COLLATE utf8_unicode_ci;
Anyway all the jcomment tables now have successfully changed their code from
utf8_general_ci to
utf8_unicode_ci. I cleaned the cache but the special characters are still displayed as questionmarks.
So, what did I miss here? Did I miss a table or why else didn't it work? =\
Thank you very much for helping out!