Comment by xenocyon

Not exactly spaces, but I have been bitten by something like this at my work quite recently. A Confluence page with special characters in the page title was working fine for a while. At some point there was a Confluence version update which made the page URL broken (and apparently unrecoverable, or at least not easily recoverable).

One way to look at it is that people of a certain generation eschew spaces because the tools of their formative years simply couldn't handle spaces - but another is that the olds have learned that generally erring on the side of KISS ("Keep it simple, stupid!") isn't a bad idea.