Ok I *think* I managed to unsplit those roads without undoing any of the other work. The bus routes still have problems, but they did before too, so no big change there.

...It's from a different changeset ( https://www.openstreetmap.org/changeset/136673392 ) but I was also wondering about this gate sitting in the middle of Lawrenceville Street: https://www.openstreetmap.org/node/10934511170