Feel free to make edits.

Do people have the impression that signing up for cryonics makes reversible vitrification much more likely?

I certainly assign it high probability (although not necessarily that it is the best way to accomplish this specific goal). The only scientists that I'm aware of pursuing the goal of whole organ vitrification are Greg Fahy and Brian Wowk of 21st Century Medicine, who are also cryonicists and whose main source of funding seems to be cryonics. Chana and Aschwin de Wolf are also cryonicists, and do neural cryobiology experiments -- a topic that is basically unheard of outside of cryonics.

My understanding was that the current vitrification process as used for cryonics is extremely toxic, but that's fine because the most likely revival process would be scanning.

I would describe it as somewhat toxic, but not on par with say fixatives. Effective toxicity is dependent on exposure time, so faster cooling is a factor there. In any case, vitrification is something we can expect incremental improvements to result in higher viability in larger organs over time.

I would expect future brain preservation research to be focused on issues like getting the cryoprotectant through the whole brain as quickly as possible, test scans of cryogenically preserved brains to see what level of detail is being kept currently, and alternative methods like plastination.

Yes, scanning is good, but viability assays are arguably better in some respects because something that doesn't harm viability is less likely to harm things that you can't detect with current scanning tech.

If you vitrify a small slice of brain tissue, the cryoprotectant can be washed out and the cells will resume functioning. I expect work that improves viability in larger organs and whole brains to involve the discovery of less toxic cryoprotectants and/or delivery of such past cell membranes and the blood brain barrier. Another approach is supercooling, which allows lower concentrations of cryoprotectant because it avoids ice formation below the freezing point.

While reversible vitrification would clearly be valuable for both cryonics and medicine in general, I think if you want more research into it you would need to explicitly fund it and you're not going to get much of it as a spillover from signing up for the current version.

That seems like a reasonable position, but it could be wrong due to network effects and so forth. I don't see any kind of public outreach designed to get people to donate money to focused cryonics research, rather I see private networking between wealthy cryonicists as being the major factor in the present environment. That's something that can be affected indirectly by an individual signing up (by influencing wealthy people in your social network to become interested), I think.

It's not just "is the effect positive" but "is the effect in the same range as the current best options". If you think it's 1/100th as much good for your money as donating to the best charity then you could count 1% of the spending as altruistic and the rest as self-spending, but I think you need to get up to at least 1/10th before this bookkeeping becomes worth it.

Perhaps, but note that the significance of x-risk overall is higher in a world where everyone lives a lot longer. So the percent to which this matters should be affected by your confidence in the soon discovery of life extension (even if you don't personally experience life extension).

What kind of utility are you thinking about? I was writing for someone with a vaguely hedonistic view, where death is bad because of the effect it has on those that remain and because it removes the possibility for future joy on the part of the deceased (if you're not at malthusian limits). A preference utilitarian will see death differently, though, as a massive violation of preferences.

I'm thinking that some kind of preference-based utility could still be considered as a total over time -- the more sentient beings whose preferences are met over time, the more utility there is.