Sorry for the late answer, in fact the next version of the Knifer plugin will be more generic and able to deal with all kind of weapons, including nades, boots, curbs...
Date of release : when it's done

However there is a dirty solution : in knifer.xml, modify the "knifeid" parameter.
<set name="knifeid">12</set>12 is the number identifying knife kills, replace it with 25 to get HE kills. The list of weapon IDs is available in the file parsers/iourt41.py (search for "UT_MOD_KNIFE" to find it).