Their CEO states:

"(proton fraud detectors) are looking for certain patterns in use. And they collect clues on the dark web. For example, if you find Proton mail addresses in criminal Internet forums, the accounts behind them will be blocked."[1]

I've never participated on a "dark web" or .onion forum but I could imagine doing so for a variety of reasons ... are there not very interesting discussions occurring there ?

I would be classified as a criminal for being part of that discussion ?

Should I be retroactively classified as such for my discussions on cypherpunks in the nineties ?

[1] https://www.nzz.ch/technologie/proton-ceo-andy-yen-wer-geset...