Shipment notification html

I would like to keep the format in the comments which are sent to the customers when sending shipment notification. Html tags I tryed to add in {$shipment.comments} are filtered and not displayed.

I'm trying without success to find out how to modifiy {$shipment.comments} in shipment_products.tpl to keep formating of the text (line feed, paragraph).

Same behavior with v4.1.2.

Actual formating is not userfriendly. Can anybody help me ?