My strong opinion is that spaces ALREADY have a role to play as a delimiter. To separate words. So, if we want to list ‘words as data’ (ie: tags) then we surely must use another character as a delimiter. This also means multiple words can be used easily too. It’s the way we already use commas when we write. So use them

USUALLY a load of words separated with spaces is a sentence. Words separated with commas are lists. So it makes sense, you see?

I also commented on Josh’s post to say:

The use of comma delimited categories has been in use in XML for longer. Databases too. Basically using *any* ‘character’ is MUCH better to use as a delimiter, because a space ‘needs space’ – know what I mean?Also spaces can be whitespace. Which is often ignored in places. Commas make sense. We are used to using to spaces list thing: cats, dogs, mice, bears. It even makes more sense grammatically, let alone programmatically.