The APPEND action has some nice underlying code which makes sure the appended text appears immediate following the bottom-most row of the subject file. Meanwhile, the APPEND_FILE patch command has nothing like that, which can result in text being added to the right side of the last row, instead of below it; or, if you try to control for that by adding a carriage return to the text to be appended, you can end up with blank lines in the middle of the subject file.
Camdawg has written a separate "Remove_Blank_Lines" function which helps with this, but lately it has been causing occasional install errors, for reasons I cannot determine.
It sure would be nice if APPEND_FILE has the same ability to handle to that APPEND has...