Deleted diff comment shows up as private contribution on profile

To reproduce:

  1. Make a comment on a code diff
  2. Go to profile to check that comment showed up under "Activity"
  3. Delete comment
  4. Profile now says "User made a private contribution"

Screen_Shot_2018-11-08_at_1.38.28_PM

This doesn't seem to happen if you comment on the regular discussion thread 🤔