(Not that I necessarily support a Georgist tax in this case, since it seems that your interest in the domain is noncommercial in nature)
E.g. if you owned and actively used greyface-.com and I'd make an offer of 10 000$ just for the fun of it, either you literally give up your name (I eat the cost but that's a risk I could want to take) or you're stuck with a percent of that to pay every month/year even as nothing else changed for you.
If you're willing to pay $10000 for it, even if only out of spite, then it's worth that much yeah. The domain is suddenly in more demand than it was, taking it out of circulation is a bigger imposition on society than it was before, so isn't it right that the tax on that goes up?
As a society I think we don't want to encourage adversarial pricing on taxes, the same way property tax isn't just based on raw demand (or even linked to it at all depending on the country) and has elements of controls to prevent too much gaming of it.
You also have to eat the increased tax going forward. Which could be spent on eg universal healthcare.
