Attempt at neutral thoughts on pricing models aside, my suggestion for a different approach would be to offer most things for free in simple forms, and paywall advanced customization.

Using the smart comment button as an example, you could include it for free with only the core expected functionality (jump between parent comments). But if I want to change the interaction, or access advanced actions like collapsing threads or something, that's locked behind a purchase.

This way people can get a taste for everything you have to offer, and the decision to spend money is shifted from "pay you to get something that feels arbitrarily disabled" to "I like this and want more" or even just "I want to support a good developer".

As far as actual cost, I don't think I'd pay more than $10 one-time for any Lemmy app right now. If you're getting what you hoped for out of this model then don't change it on account of one angsty thread - but if any of this rings true, you could consider pricing for early adopters at a cheaper "early bird" price as one option, to build goodwill (making us more likely to want to support you down the road).

Or the other option is to follow Apollo's (RIP) model, with a one-time mid tier for upgrades of basic stuff, and a subscription/larger cost for more unique features/things we all know cost money on an ongoing basis/the subset of people who just want to support you.