Agreed, there should be a note text under the field that says "letters only" or something to that effect.
In the longer run... this field itself is actually kind of a problem. After the user enters it, it's invisible to them forever after, and the only time users interact with it is in URLs and in CSV files.
We should change this field to be auto-generated in a similar manner to how we auto-generate default clean-url titles.
Agreed, there should be a note text under the field that says "letters only" or something to that effect.
In the longer run... this field itself is actually kind of a problem. After the user enters it, it's invisible to them forever after, and the only time users interact with it is in URLs and in CSV files.
We should change this field to be auto-generated in a similar manner to how we auto-generate default clean-url titles.