In RFE 880487, along with a request to display signautes while
composing, Michael Gsandtner made the following suggestion:
You might add macros like %U expanding to the user
signature in templates, or %O expanding to the original
message with the ">" at beginning of each line (may be
with the message citation improvements of #832217).
A template might then look like:
"Your request was successfully completed.