I went to MSOE after growing up in Southern California. Bubbler was a key way to identify those from Milwaukee and immediate surroundings. It's such a precise locator; even more so than calling I-5 the 5, just as accurate, but the 5 gets you to like Santa Barbara and south, where bubbler cuts off just over the Milwaukee county line. A Racine native drinks from a fountain like everyone else; Brookfield natives might use a bubbler.
I moved to Milwaukee a couple years ago. I can confirm this is a thing, and it's very weird. I've got a friend from Reedsburg who says it's common there, too.
As soon as I saw that comment in the Reddit post, I clicked on the guy's profile to see if they're from Wisconsin. Wasn't obvious at a glance.
Bubbler is used in many parts of Wisconsin, it isn't just Milwaukee by any means. I grew up in Brillion (2.5 hours north of Milwaukee) and everyone there (and the surrounding area) calls it a bubbler.
https://www.reddit.com/r/AustralianBirds/comments/1kjve1q/su...