For us that were around when the default changed from mutable to immutable cons cells, known the rule "just prepend an m". I agree that the link in section 4.10 can be improved - but calling it "obfuscation" and "deliberate" is taken it too far. File a bug report, and I bet it will be fixed.
'mcons is part of 'racket/base. 'mlist is part of a library that contains two layers of warnings, is not linked to by the Racket Guide or Racket reference and lives under the 90th of 96 links on the Documentation page. It's lower in the great chain of being than "Unstable May Change without Warning".
(cons 1 (cons 2 (cons 3 '()))) is commonly required in the Racket family of languages for purely pedagogical purposes. That it is the only pattern for 'mcons provided by 'racket is a deliberate statement of community values in regard to mutable lists.
In regards to filing a bug report, the bug is that there is mention of mutable lists and a hyper-link in the documentation for the Racket Language. Because mutable lists are not part of the language the bug fix is properly removing the reference - at least in so far as maintaining consistency with the rest of the documentation because other libraries are not cross linked from the Guide and Reference. Linking "mutable lists" to 'compatibility/mlist, would just replace one bug with another...unless leaving 'mlist out of 'racket/base was itself a bug. That that is the case, is unlikely.
