I think we should respect an individual's preference of signing off a
letter/e-mail. I find it odd for anyone to make a comment about it.
It is the first time I come across this in a public forum.
Jou is right that in the Theravada tradition, few members of the
Sangha uses "Venerable" to address themselves. Although I am not in a
position to discuss this issue, I don't see anything inappropriate or
against the Theravada tradition.