NeoDB

I may be biased but I find the idea of Threadiverse integration more intriguing. ... I miss the old IMDb message boards where even the most obscure film had somewhere you could discuss it without it being lost in the mix.

Totally with you on this! And as you discuss, sorting that out and how it federates seems to be the big challenge (and big promise).

Your idea seems great but I fear it would involve some protocol hacking and quickly run into compatibility issues (though I really don't know).

I do wonder (and I may have suggested this already) if a good way to go would be to create an activitypub group/community for each item to which anyone can post. The AcitivityPub backend NeoDB is using may not support groups, in which case I'd wonder if using lemmy as the basis for groups somehow would be feasible.

I don't know how well that'd work over federation though. Taking your example, you could cross post to the 1984 item and a general literature community, which should achieve the same thing (and perhaps more if cross post viewing were ever improved).

Subscribing to item-communities from a platform like lemmy wouldn't make too much sense as there'd be too many and it'd be unwieldy ... but that's where the single sign on comes in ... you'd just go a NeoDB instance for all of that to be well organised. Though perhaps NeoDB could generate aggregation multi-communities for multiple items and federate that out as a group, which would be pretty useful for the fediverse as a whole.

From a comment around here on NeoDb, from someone who'd asked the lead dev about lemmy support, they seemed interested in the idea of implementing groups somehow, so it may be fertile ground.