Afaik they were from random new accounts like all the messages. I wasn’t part of the community but I remember that it was decided to not discuss the fediverse chick topic on our instance anymore. Since only the people from within the community got those messages it was assumed that the person who sent them was either part of it teaching what happened within this community. So starting it seemed to be sensible and it seemed to have worked.

Edit: found the post about the instance decision. (English version at the end of the post)

We had a community for the fediverse chick on our home instance. That went pretty bad, pretty fast. People there tried to find out who she is and where the spam is coming from. They ended up receiving disturbing gore in their DMs…

Thanks for adding that context!

Your first tries on spot cleaning look to me like the canvas was painted in white. So I’d look for options to clean paintings and maybe retouch the spot you tried to clean with white paint.

This seems to be a pretty detailed guide.