Allow comma's in permitted file extentions

Form a usability perspective I expect a CMS to do the work for me. Right now, on the "Permitted upload file extensions" settings, I get the description:

Separate extensions with a space and do not include the leading dot.

So I entered pdf, doc, xls, ppt, zip. No dots, so all accepted.

After uploading a file I get this error:

The selected file filename.pdf could not be uploaded. Only files with the following extensions are allowed: pdf, doc, xls, ppt, zip.

It took me a while to figure out the comma's in the allowed extentions where the cause of this error.

Suggestion:
- Filter out comma's automatically
- Or (quick win) change the message that dots AND comma's are not allowed