Here's the link to the post:
I2P: http://hkpahyrrlq2fuxjlmcnpf7e47jdnciy7ageciehhyclu2yld7xha.b32.i2p/res/7.html
Tor: http://mnj2jsmwbgzhbccunvcyw7frpinmquqfazfwlc4jqrczbjs74m5lg7ad.onion/res/7.html
I got quite a few responses considering how small the userbase (likely) is.
The summary of it is, that it uses Javascript, therefore honeypot and that it's too similar to the Fediverse (even though the post explains it's not lol, I copied the post from Lemmy).
I've actually been having a discussion with a BitChan dev about why Plebbit is more spam-resistant than Bitmessage.
The summary is that it effectively has no captcha system as the captcha system only applies to the website and not the underlying protocol.
If someone's interested, I've attached a screenshot.
Plebscan