GPX upload rejected with "Tags is invalid"

I attempted to upload a track from Luang Namtha to Huay Xai, Laos, tagged “luangnamtha, huayxai”, and was greeted with the following uninformative message:

There were problems with the following fields:
* Tags is invalid

Perusing the Upload help page indicates that commas are not allowed, and you’re supposed to use spaces instead. How hard would it be to a) change the error message to say so, or better yet, b) just change those commas into spaces then?

I don’t know, but you should create a ticket in the TRAC website or noone will look into this…