Just a quick note about comma seperation in a URL:

The standards state a comma (,) character is reserved for special use in URLs, whilst they don't tell what the special use might be. As well the practical use of comma in URLs is much less strict. Many CMS use comma seperated lists in URLs to pass information to the URL target.

One of the main reasons for using comma is search engine optimization (SEO). URLs containing many parameters (e.g. www.example.com/index.php?param1=xxx&param2=yyy) should get rid of their parameters (even if I know that became less important today) by converting them to someting like www.example.com/param1,xxx/param2,yyy ...this is where commas are often used, exactly like in the example.

After a quick research about this I had to come to the conclusion that it's absolutely okay to use comma for parameter seperation this way.

Please note: commas are allowed inside the filename part of an URL but are strictly not allowed in the domain part. It's not possible to register a domain name containing a comma. For sub-domains it might be technically possible, but I wouldn't recommend it.