This page is part of the web mail archives of SRFI 1 from before July 7th, 2015. The new archives for SRFI 1 contain all messages, not just those from before July 7th, 2015.
The sentiment seems clearly in favor of staying with ! for the suffix
character marking linear-update procs in SRFI-1. I concur, as well.
Time to write up the SRFI.
-Olin