Arno,
Just being an anonymous naysayer does not further any cause.
Likes are not anonymous in Groups.io - you can click on a link to see a list of who liked the post. I would expect that unlikes would not be anonymous either.
I don't know if that affects your evaluation of the proposed unlike feature, but it may tend to reduce the willy-nilly use of unlike.
Shal
Shal Farley