Should Emacs byte-compile an already byte-compiled file?

[Andrew M. Scott]

Should CVS Emacs byte-compile a byte-compiled file?

I had downloaded some updated elisp packages, and due to some
sloppiness on my part with Dired marks, I ended up byte compiling

psvn.elc

and getting

psvn.elc.elc

Thoughts:

Perhaps the byte compiler could have noticed the .elc extension or the
header line starting with 
;ELCXXXXX
and not byte-compiled this file, or asked or automatically byte-compiled the 
*.el
version instead?

Thanks,
Andy Scott