OK I just got a reply from the software authors: they can't fix it until a patch comes out. To rephrase what they said:
"This is a bug in the current software version and we will fix it in the next version."
That means there could be a long wait. Next, I'll ask in the relevant forums to see if someone can code up a plugin as a temporary fix.
Until there is some sort of solution, can I suggest that you:
1. Ensure that Like notifications is off in your Settings - it works for some people for some reason.
2. Filter your email notifications: first create a subfolder in your email client and name it Likes. Then take a unique factor in the subject line, the from line, or the body text of the Like notification emails, and use that to create a filter. Make the filter send the emails to the subfolder. Now you won't see them in your Inbox.
3. Ignore the Like notifications as best you can in the PM Notification box or pop-up.
Best I can do right now
