Yes, you are running into that limitation, and I told you how to get around it; escape the special characters instead of using them literally.
//tokenize 32 a $chr(124) b $chr(124) | echo -a $1-
Note that this limitation is not unique to mIRC. This is the same issue as in the regular expression syntax. For instance, you cannot have the regular expression matching  without escaping the  characters, since they have special meaning in regex syntax. The means for escaping in regex is \[, in mIRC, it's common to use $chr().