I'd also like to know.

I'd also like to ask people not to block this way. It creates LOTS of false positives. There's much better ways to handle bots and this tactic seems particularly dumb for Reddit given they want users from places like China or elsewhere where a VPN might be required. Not to mention people using public WiFi. It's not like VPNs are uncommon these days.

If you must ban IPa then do so with a timeout and easing function. So that each hit results in a longer ban time. Bots want to move fast so even a few seconds ban time will make them switch IPs while not impacting most users (who will refresh)

From my experience, PIA VPN and Proton VPN also get blocked everywhere, from Reddit to captchas on Google Search.

PIA it’s one of the least trustworthy VPNs, highly recommend getting a different one.

They purchase residential traffic exit from botnets.

Any proof or articles you could link to backup that claim seems unlikely given their size/reputation also would be surprised they’d get blocked this often using botnet traffic

The person you're replying to is claiming that providers other than Mullvad avoid the being-blocked-by-reddit issue by using residential IPs.