unmark all in ibuffer

[Xah Lee]

ibuffer's keybindings are i think designed to be compatible with
dired.

However, by habit sometimes i press “U” trying to unmark all, but it
gets me ibuffer-do-replace-regexp instead.

Does anyone know:

• shouldn't U be the key to unmark all as in dired, instead of the
“**”?

• what does ibuffer-do-replace-regexp do exactly? the online doc
doesn't say so much.

Thanks.

  Xah
∑ http://xahlee.org/

☄