better yet, get rid of the comments all together. having no comments saves you from having to moderate them and it's just not worth it. if you're writing anything tech related and worthwhile you can just proxy the discussion to HN ;)

Not really a great option. People only really see stuff on HN that's relatively fresh so anyone coming in after the initial wave of engagement dies down won't see any discussion.

Also you can't discuss on old content anyway. It's blocked.

Yeah, somewhere around 2 weeks after a post they completely seal the comments on HN.

There are other techniques that do a reasonable job at stemming the flood. The "hidden field" technique still reduces spam by quite a lot.

I wrote about another technique at the end of my own captcha rant: https://inimino.org/~inimino/blog/kill_captcha

The proposed solution would replace captcha entirely, but to my knowledge nobody has tried it.

How about different revocable secret keys to your mailbox given only to those who you wish to contact you

If people have to request to be able to contact you, it is not a public inbox anymore. This is the way most walled gardens work, you have a separate step before you can interact, so it works, but it lacks some of the affordances of the public inbox model of email or blog posts, such as allowing anonymity.

From experience, Akismet works well, so reCaptcha is not the only anti-spam measure that works for WordPress.

For WordPress there are plugins like Akismet (a service), Antispam Bee (local), etc, that are pretty good at filtering spam without the need to display annoying captchas.

While sending comment bodies to these services :) what a privacy