I find a vi search for [('"] allows me to verify the closing parens with % and count the quotes in and out. Figureing if the ) is in a different quoting space can be a problem. Good structural indentation helps identify quoted areas. Note that case statements can have wild card starting with ( so they do not confuse %, although case traditionally did not use them. If you have isolated () in character or string contexts, you can temporarily replace them with substitute strings like '~oparens' and '~cparens'. (The ~ is the rarest ascii visible glyph.)

You cannot blame tcsh or bash for the fact that exec() obeys the magic line. It is nice that you can ensure your scripts use the designed interpreter. If you source a file or feed the file to stdin, the magic is ignored (no exec()). You are even allowed one argument on the magic line, so you can say things like "#!/bin/awk -f" or "#!/bin/sed -f" and make scripts for tools not normally considered script interpreters. It saves a fork() and exec() over a shell script calling awk or sed.