That’s fine. If the simulated screenshot would be wrong in any of these places, then by all means the name
should stay as is. For the features that are using a semicolon, however, it’s clear that the mapper’s intention was not for the user to see a semicolon. If Americana is avoiding ugly breakage, then you’ve written a better headline than I was able to come up with.

I certainly don’t think that it is a particular good idea when a single data users imposes a format for a tag that breaks pretty much everybody elses map.
Can you elaborate on what’s broken as a result of Americana or any of these other data consumers (plural) interpreting a semicolon as a value separator? Americana still renders slashes, dashes, and spaces as slashes, dashes, and spaces. If you’re concerned about semicolons getting misinterpreted, so far, I’ve come across only one name
in the whole world that properly contains a semicolon in the real world – and it’s escaped as ;;
. So if anything, that feature is broken in any data consumer that does not interpret the semicolon as Americana does.

full route descriptions (any PT route)
This would be grist for a separate topic, about which I’m pretty sure you and I would see eye to eye.