Is it a standard to use the '+' sign instead of %20 for tags with spaces?

For example, a tag "Creative Commons" becomes /tag/creative+commons in b2evo.

I'm not an expert with microformats (I ignore it for the most part, I just re-read it when I need to use it), but isn't /tag/creative%20commons better? Search Engine Bots reads %20 anyway.

Or maybe, (which I personally think is much better), change spaces into underscores? So instead of '+' we'll have /tag/creative_commons

Just a random thought :p The plus sign is kinda awkward or out-of-place or have a different meaning like "all posts with tags 'creative' and 'commons'" :p

Thoughts?

Should we change from '+' to '_' ??