If you "Sign with MFA" and only add a comment, we can produce a weird notification and feed story. Hide these stories from feed since they're broadly not interesting.
- rP612e9c6e09ad: Hide "Signed with MFA" stories from feed
- Used "sign with MFA" and only posted a comment.
- Observed feed.
- Before: Janky "untitled story".
- After: Sensible "added a comment" story.