[Based on feedback from Marc Feeley.]
Currently symbols can either be delimited with pipes |...| with optional hex escapes inside, or include hex escapes directly without the pipes. This wastes two characters that were reserved in R5RS, the pipe and the backslash, when either one by itself would be sufficient to represent all symbols. This is especially unfortunate because both characters are used as extensions in various Schemes - the pipe being another symbol character in SCSH (to represent shell-style pipes and C-style operators) and the backslash used in Gambit's infix syntax. We should reconsider if we really need to take up both of these characters.