Filter table dynamically with slicers

Yes, this should be doable, what you need to do is create a Measure that checks if those two columns (date and customer) are filtered and if they are select the comment otherwise show blank.

Measure structure should resemble:

Comment_Measure =
IF( ISFILTERED(INSERT DATE COLUMN), //Date filter check.
       IF( ISFILTERED(INSERT CUSTOMER COLUMN), //Customer filter check.
           MAX(INSERT COMMENT COLUMN), //Both were filtered.
           Blank() //Date was filtered but Customer wasn't, you can change this to a default 
                       //message like "Select Date & Customer for Comment"
       ),
       Blank() //Date wasn't filtered, you can change this to a default 
                   //message like "Select Date & Customer for Comment"
)

Now drop that Measure into the card. Keep in mind that this is assuming you only have one comment for a customer in a month, you would need to add more logic to grab a list for example if you have more.