An error occurred while saving the commentPierre Fontana commented
It is actually possible to delete a comment in a task:
1. Browse to the underlying sharepoint site
2. Click the Conversation link on the left menu --> This will open OWA on the group email
3. Search the inbox for the email with task comment to delete
4. Expand message (if needed), then click 'More actions' and select 'Delete'
Hope this helps