Should this be this way?

[Linda Walsh]

My login shell is /bin/bash (i.e. not /bin/sh); SHELL=/bin/bash as well.
Typing 'which bash' gives /bin/bash, and whence bash: bash is /bin/bash.

I had the foll0wing script which acts differently based on
whether or not it has a #!/bin/bash at the top: (i.e., as it is
displayed below, it fails; one need remove the [] from the first
line for it to work.
================
#[!/bin/bash]
while read fn;do
  base=${fn%.*}
  if [[ -e $base ]]; then
    if [[ $base -ot $fn ]]; then echo "compressed version ($fn) seems newer"
    elif [[ $base -nt $fn ]]; then echo "uncompressed version ($base)
seem newer"
    else echo "both versions ($base) are same age"
    fi
  else
    echo "No uncompressed version of $base exists"
  fi
done < <(find . -type f -name \*.[0-9].\*[zZ]\* )
-------------
The error:
./manscan.sh: line 12: syntax error near unexpected token `<'
./manscan.sh: line 12: `done < <(find . -type f -name \*.[0-9].\*[zZ]\* )'

Why would this script behave differently if the first line
exists or not?  (Putting the !shell in square brackets,
made it a comment, not an interpreter spec, thus the same
effect as if it wasn't there ('cept the line number of the error is 1
less if you don't have the line! ;-)).

So...is this correct behavior for some[inane POSIX] reason? 
Seems a bit odd to me.