in the OTRS Version 3.0 we have created a new skin for customer frontend (.../otrs/customer.pl). Next we have enabled further columns in the CustomerTicketOverView.dtl.
It works good. The data in the new columns can be sort up and down.

Unfortunatelly title of the sorted column has no sort sign. There are neither up nor down arrow.

Has anybody an idea where this property can be configured?
thank you for your assistance.
regards
yury