Folks:
Just been thoroughly studying the help for 3dvolreg, and the README.registration file.
Looks to me like at some point the help text got butchered.
1. All text from the line
"3dvolreg -twopass ..."
down to
"See program 3drotate..."
probably is wrongly inserted and belongs somewhere at the end. Part of this looks like it's intended to be an example like in README, but seems incomplete.
2. The text following that, from
"The following options can be used to control the iterations"
down to
"weight brick in the final registration pass."
can then be out-dented (and less-tightly wrapped) to align with the main option listing above.
Hope that helps,
Graham