The UX isn't degraded at all, and it isn't unexplained either.
It's thoroughly explained. ^^^^
I'd always assumed that the majority of systems didn't see the forward slash as a delimiter in queries. I thought it was common knowledge to stick to commas. Meh.
So we're accepting a degraded user experience because of an unexplained quirk in the chosen technology?
If that was the way we did it we'd still be butchering vBulletin.