I often trip myself up by using semi-colons instead of commas when 
entering multi-item nosy lists in the web interface -- a muscle 
memory imposed by our use of Outlook for email, which insists on 
semi-colons to separate multiple email 
recipients.

Allowing both semi-colons and commas as 
separators -- and transparently converting semi-colons to commas 
on input -- would be kinder to Windows-based idiots like me.