... produces:=for comment Comment! =cutSECTION Comment!
That is the correct behavior, your conclusion "=for comment hides text from perl but not perldoc" isn't correct. From perlpod (emphasis mine):
The command "=for formatname text..." specifies that the remainder of just this paragraph (starting right after formatname) is in that special format.
Remove the blank line after the =for and the "Comment!" is hidden. The =for still begins a section of POD that needs to be terminated by =cut, so Perl will ignore the entire example you posted.