I've added a new feature that should let course authors/contributors change commas to semicolons in whichever courses need it 🙂
To access the feature, go to the course's Edit -> Vocabulary page and click the button at the top right of the course:
Then click the "Replace commas with semicolons" button:
You can then double check any changes that were made. You'll need to save the course for the changes to take effect.
Note that this feature also changes any semicolons in a course into commas. I think this is what's desired in most cases, so that sentences that already have semicolons don't get broken, but if you run into a case where you need semicolons changed to commas and existing semicolons left as they are, just let me know 🙂
