The comments too are less helpful than usual. A lot FUD and anti-EU sentiment (which may or may not be warranted, but there's very little objective reasoning going on).
Addendum: yes, people could look it up, but given the strong call to action ("last chance to fix eIDAS!"), I would suggest that the onus to provide clear information is on the authors. You can barely get people to care about privacy at all, let alone when so little information is provided.
Also brief info about website (for the ones who doesn't want to visit an unknown domain without knowing):
A Mozilla website for open letter by 300+ cyber security experts, researchers and NGOs.