The best way to protect dissidents would be not to ask unnecessary personal information like phone numbers. Sadly, it is difficult to find a messenger or web email service that doesn't require it.
If you get 10k new accounts in 5 minutes and they're all from some VoIP provider in a tiny corner of the second or third world, you have some data to work with there.
Maybe I am too charitable.
The site has also been around for over a decade, lots of opportunity to accumulate.
I mean, if you're a dissident in a country with a violent government, maybe don't use the service that requires personal information?
It seems a bit much to me to say no service ever should require people's phone numbers because somewhere, someone might make a bad decision and use the service when they shouldn't have.
Maybe SV should try to innovate more instead of reverting to "Wow, sucks to live where you do; hold my craft beer" so much these days.
The internet was supposed to set people free. It's not working.