Because technically I think we could have that and maybe it would make sense and then this would not be the bug but the error message would be it instead.

Spaces in tags would likely lead to confusion in the editor -- when you type a space and there's no match, is that the end of a proposed new tag or a space in the middle of an existing or new tag? I think our intent was to not allow them and this is a bug.

Monica Cellio‭ given that tags are pretty clearly delimited in the editor, I don't think that there would be much confusion.

Trilarion‭ we could technically have that (in fact, we used to before the no-spaces rule was put in place) but for whatever reason that got removed (I forgot why since it was some time ago)

We can technically for sure, otherwise people wouldn't be able to suggest them in edits. I kind of works.

To avoid confusion in the editor, one could delimit tags by comma and strip leading and trailing spaces but otherwise leave tags as they are. I don't think there is really a strict technical restriction available.

If we ever used tags as part of URLs we would have these slightly annoying %20 in them, but that also can be circumvented (replace space with "-" in URLs for example).

It really comes down to: Do we want them? Need to search for a corresponding discussion and if there is none, open one.