[Kalium]

Nah, it was released back in 2017. I've seen it discussed periodically ever since.

The issue with just doing memory-consuming work client-side is that it only marginally slows down spamming. Spammers tend to use compromised machines they don't own. Unless you can make it prohibitively expensive to calculate something using machines you don't pay for - perhaps not a trivial ask - you wind up needing a different set of tools. This is why Google tends to look at things that will exhibit human variation rather than pure computation.

It's not that your ideas aren't good. I'm sure ARGON2 has a use here! It's that this might not be a problem easily solved by consuming more resources.

[xiphias2]

Cool, I'll try it out the next time I have a problem with using TOR. You're right that ARGON2 doesn't help if CPUs/RAM are free, it just makes parallelization hard.

[Kalium]

Parallelization is easy if you have a botnet of millions of machines owned by others to draw on.