Because it seems that the likes proposed by graphcomment are just for comments?
I’m really looking for a Voting/Downvoting system as can be seen in “New Features Voting Systems” for open source software for example.
Doesn’t sound like GraphComment will be the thing you are after then. There is a demo on https://demo.graphcomment.com/en/graphcomment-demo/ which shows the ‘voting’, but it is based on Comments. Sounds like you might need someone else’s help on this site for your request. You could have a look at https://www.upvoty.com/ it’s a 14 day trial, maybe that might meet your needs.