I suggested an idea to fix this, that I called "thread entanglement". I had suggested it for Kbin specifically, before, but honestly the base Lemmy software could use something like this. I'd love to see some sort of smart merging of duplicate threads like this be possible.
As others have mentioned in that thread. It would be better as an option from the user side rather than site wide forced implementation. I hope you open a GitHub issue/discussion in the repository so the idea could get more exposure.