2) Why would someone use this? Right off the bat I don't get why I should use this instead of email. In order to start a discussion I need to know the email addresses of the initial participants whereas newsgroup or mailing list posts go out to hundreds or thousands of people I may or may not know ahead of time. If I need to know exactly who's going to be involved from the start it's easier to use my mail client.
I understand that the discussion can be made public on here, but what's the point? Sure, you don't need a newsgroup already set up, but a newsgroup is also a good starting point for someone looking for discussions about a particular topic. I just don't understand what need this is fulfilling. This needs to be made clear on the front page so potential users don't navigate away 15 seconds after landing on it with the impression that this is a reinvention of the wheel.
[edit] There's a small grammatical error on the About page. "Discuss any topic with lot's of people right now and waste no time for registration." should be "Discuss any topic with lots of people right now and waste no time for registration." "Lots" is plural; "lot's" is possessive.
That said, you bring up a valid point about reinventing the wheel -- GMail does this already with conversations. So this app would need something more.
One idea off the top of my head is to enable people to participate in a discussion using an account on the site, rather than through email. Maybe also allowing people to comment on public discussions, but giving their comments a lower priority (along the lines of HN's prioritizing of comments).
The email that I got was in plain text. Maybe there could be an option when creating the message to send the emails with formatting? That way, if you know that your friends can see formatted emails, you can send properly colored code.
Comment posting is very quick. When I sent in a comment through email, it took about half a minute for the comment to show up -- but I guess that's to be expected.
So, my general verdict:
I like the idea.
However, I think that for it to appeal to non-hackers, it should support formatting. It could even be something simple, like the italics supported by HN.
Sending emails in HTML is a big question to me. I believe that people who would prefer HTML emails to plaintext ones would also prefer web-interface to email-client when posting new comments. What do you think?
Another improvement you could make to the code display is to display the language in which the code is written.
At work, a short comment in an email can very quickly build up into a large and complicated discussion. Lots of branching, occasionally hitting reply instead of reply-all, really a nasty mess. Part of the problem could be that I'm used to gmail and at work I have to use outlook, but I digress.
I think it would be really cool if once an email conversation kicks off, if I could send the entire thing to a resubj email address, and have it automatically build up the conversation up to that point. Then, the conversation could continue in resubj. If you implement this, or it is already in place and I missed it, let me know and I will start using your service immediately.
edit: also, if you set up some kind of api so that I could embed conversations on other websites, that would be kinda cool.
It's quite a fuzzily-defined feature, because people don't always quote entire messages, they can change messages, and the characters used to mark off quoted text vary between email clients. However, it would be a cool feature to implement, maybe as an optional thing.