This bug points out a bug where if you spam-like a topic, it will become a negative number eventually.
It seems like this bug is known from the forum I’m currently in. People abuse this just to ‘downvote’ posts, however, if you reload, the bug would be fixed and it was only visible to the person who spammed the like button anyway.
Will this be fixed in the future?
There are no negative likes in Discourse core.
That’s a big part of why they aren’t in Discourse core.
Whoever is running whatever site it is, is using some plugin that implements those. It’s pretty likely that it’s working as expected.
You’ll need to convince the site admins that it’s a problem that they want fixed. If it affects only the user who is downgrading the post, it doesn’t seem like much of a bug.