Unfixed for 1 year, not years. I've got an instance of Commento running on two of my sites and haven't run into / heard of this issue on Firefox. Though I'm not using the Docker image.

Maybe give better steps to reproduce the issue, as it seems to only be happening to one other person?

It does seem like Commento's development has lost its momentum (last commit was 6 months ago). The author likely isn't getting more funding from Mozilla and is focusing on their primary money-maker, the cloud-hosted service.