While I am delighted that nitter is back and maintained, we cannot list it yet for the reason that @anon29374801 already mentionend. We cannot really list software where its maintaince is uncertain. People shouldn’t have to check the PG website every week to see if they are still up to date.
We rather wait to see if a project is truly able to stand on its own for a while to be listed. This way when someone chooses something we recommend, they can have a certain guarantee that it is not going to dissappear tommorow.