I don't know if there are more to this or if it would break some other rules but as of my testing it should be fine to remove this rule for headers that have no sorting applied to them.
This is the case already for "normal sized" tables as the padding-right rule is only applied if there is a sorting class to the element. But it has been forgotten for the table-sm variant. So there are two options that I can see.
Specify this rule does not apply if there is a sorting_disabled class
Do the same as what was done for the normal sized table in the following commit: 4e611f31ff84deae5ae4666c7ba60ad8cb1012c3
doesn't effect the DataTables demos since the inserts all have values
for this field. It is done for Editor which can use this table for
editing and it simplifies the MySQL aspect.
