@Arathorn would be an objectively better person to discuss this, but the Redditor isn't completely off the mark: metadata is (currently) not nearly as well-guarded on Matrix compared to Signal.

However, work is ongoing to improve the situation; more importantly, Matrix is a different threat model (in my opinion), and allows for different trade-offs.

When I use Signal, I have to trust Signal's servers and their admin team. With Matrix, we get to keep trust circles smaller (friends and family on smaller servers, where we already trust the people running them). We have no hard requirement to federate either - if I want something just for people I know, we leak less data than Signal does to the outside world. We also get to host Matrix servers in areas we're comfortable with, whether that's our living room, or any nation that isn't America.

Matrix isn't perfect, but I appreciate how quickly they're improving, and the areas they're focusing on.