I happen to enjoy small talk, now that I'm good at it.

A cultural bias.

Well, sort of. It's genuinely useful for accessing some things our culture restricts access to. Like friends, good conversations (often people won't talk to you seriously, in person, at first, until they feel more comfortable with you. internet forums often do a good job of circumventing this though) or sex. It's a lot easier to get sex if you are good at small talk. And if you genuinely enjoy it, that helps even more. People like genuine conformists because they do a better job of conforming! (Usually. Faking it is so much harder, and takes way more skill.)

I really value the ability to have conversations with people I disagree with, because the last thing I want to do at this point in my life is shut off my opinions to change.

I'm not trying to filter by disagreement. I like to find people who agree because I could use more of those, and I do have enough access to people who disagree (it's no trouble at all to come here, or many other forums, and find people to disagree with me).

Talking to people I disagree with isn't so hard. I spend a lot of time debating with people who don't agree with me. And I can even be non-confrontational if I want to. Sometimes I go to new groups and just listen for a while to see what they are like without being disturbed. But I've been familiar with Less Wrong culture since before the Less Wrong website existed, so I'm not missing anything but interfering with the normal culture here (besides, if I want to know the normal culture, I can just go read the Sequences and other static content. or just stop posting and lurk on new threads.)

I want to I can ease that into the conversation without necessarily provoking a confrontation

Too much work to help one person, who probably doesn't want your help, and won't appreciate it, IMO.

I am fairly good at this face-to-face, but the subtle emotional cues don't carry through to online posting so much

I'm actually better at picking them up in text than IRL. It's a different skill. I practice it in text a lot. I've been known to, when I get bored with low quality content from people, start replying with little but psychological analysis of their posting. They'll usually reply a few times before they stop speaking to me, and I can get good feedback about how much of my initial guesses were correct.

I hate confrontation

You could change this. It's not human nature. It's not your genes. It's a cultural bias. A very common one. And it's important because criticism is the main tool by which we learn. When all criticism has to be made subtle, indirect, formal, filled with equivocation about whether the person stating it really means it, or various other things, then it slows down learning a lot.

I have this annoying tendency to care about anything that anyone says to or about me.

You know, Feynman had this problem. He got over it. Maybe reading his books would help you. One of them is titled like "What do you care what other people think?"

Not caring isn't just his advice. The title is something his first wife often said to him, because he had a problem with it. She kept reminding him. He got better at it eventually. It wasn't easy but he did it.

but being amenable to changing my own mind in response to their arguments (if valid) works better than upfront confrontation.

I am open. One thing is you're seeing is me after 10 straight years of online debate. It's gotten to the point that I rarely am told any argument I don't already know by a stranger. Early on I changed my mind a ton. It got gradually less frequent. I like to be wrong, I like to concede debates. I enjoy conceding. I'm tired of not losing debates; it's dull and I learn less. It's so much fun to be like, "Oh I get it now! That's even better than what I used to think!" But, well, there's no easy solution to getting more of that.