Some events, like ON TEXT do allow the usage of #,?
If you look in the help file under /help ON TEXT you'll see that it shows
Format: on <level>:TEXT:<matchtext>:<*><?><#[,#]>:<commands>
The fact that the <#,[#]> indicates that more than one channel can be specified, and the fact that the ? is listed as a separate option, means that the two can be combined, as opposed to the format for ON INPUT which shows as
on <level>:input:<*#?=!@>:<commands>
which indicates that only one of those options can be used at a time.