Undoing of votes would be nice. It's so easy to make an irreversible mistake.
We're definitely open to that.
Being able to link to a specific comment, with a context history. Right now, I can link to a comment, but you have to keep clicking "parent" to understand the full conversation.
As an occasional Reddit user, I find that particular feature rather confusing. If anyone wants to suggest a "native" way to do it on HN, i.e. that would fit with the existing design and be simple and intuitive, please email hn@ycombinator.com and we can talk about it offline.
I personally find it annoying when I follow a comment parent by parent only to have to find the original comment somewhere inside what turns out to be a really large thread. Something as simple as having a link to the original post in each comment might help navigation a bit too.
how long does it take to write a comment collapser? -_-?
I'm sure most people here could do it in a couple hours or a weekend.
And they have; there's an extension for it. But it would be nice if it were baked in.