Scheme used to use #!true and #!false before abbreviating to the unfortunate #t and #f syntax, which look far too alike.
We probably can't remove these, but we could add them back in as aliases (optionally without the "!") and hope to remove the short versions in R8RS.
WG1 decided to make no change here, accepting #true and #false but not #!true or #!false.
WG1 accepted this proposal.