Ubuntu – ‘chmod u+x’ versus ‘chmod +x’

This answer completely ignores the request in favour of addressing the how you contact the right people to make a feature request in an upstream project.

This request is already been asked and rejected. The behaviour is already possible through existing mechanisms (see the comments on your question).

For the best way to get something like that under the nose of somebody who makes the decisions, you need to find out where a package comes from. Start by tracking down the package for the command:

$ dpkg -S `which chmod`
coreutils: /bin/chmod

Then look at the coreutils package details:

$ apt-cache show coreutils
Package: coreutils
Essential: yes
Priority: required
Section: utils
Installed-Size: 5920
Maintainer: Ubuntu Developers <ubuntu-devel-discuss@lists.ubuntu.com>
Original-Maintainer: Michael Stone <mstone@debian.org>
Architecture: amd64
Version: 8.20-3ubuntu5
Replaces: mktemp, timeout
Depends: dpkg (>= 1.15.4) | install-info
Pre-Depends: libacl1 (>= 2.2.51-8), libattr1 (>= 1:2.4.46-8), libc6 (>= 2.15), libselinux1 (>= 1.32)
Conflicts: timeout
Filename: pool/main/c/coreutils/coreutils_8.20-3ubuntu5_amd64.deb
Size: 2477552
MD5sum: 7ebb74af562ad4b6f3c767f9a94e54fc
SHA1: 8afa0e8aff4bf33d946d1c301a2aa4b250e702f9
SHA256: e54ba21d60d20594e33e4fe2569621ed1312198014a81c7592934ed8dbb85ba0
Description-en_GB: GNU core utilities
 This package contains the basic file, shell and text manipulation
 utilities which are expected to exist on every operating system.
 .
 Specifically, this package includes: arch base64 basename cat chcon chgrp
 chmod chown chroot cksum comm cp csplit cut date dd df dir dircolors
 dirname du echo env expand expr factor false flock fmt fold groups head
 hostid id install join link ln logname ls md5sum mkdir mkfifo mknod mktemp
 mv nice nl nohup nproc od paste pathchk pinky pr printenv printf ptx pwd
 readlink rm rmdir runcon sha*sum seq shred sleep sort split stat stty sum
 sync tac tail tee test timeout touch tr true truncate tsort tty uname
 unexpand uniq unlink users vdir wc who whoami yes
Description-md5: ca29325ab0239421f7b6be11369cc121
Multi-Arch: foreign
Homepage: http://gnu.org/software/coreutils
Description-md5: ca29325ab0239421f7b6be11369cc121
Bugs: https://bugs.launchpad.net/ubuntu/+filebug
Origin: Ubuntu
Supported: 9m
Task: minimal

Launchpad and Debian are red herrings here. They're very downstream. The project is a GNU one. The Homepage link is a good start here: http://gnu.org/software/coreutils

On there you'll find the various mailing lists you'll need to convince people on, as well as bug trackers (but I'm not sure how they'll take a feature request - check the rules first).

Since you're specifying all the read, write and execute bits, there's no difference.

The difference comes if you only specify some of the bits:

$ umask 022
$ touch afile ; ls -l afile
-rw-r--r-- 1 jackman jackman 0 Aug 21 11:23 afile
$ chmod u+x afile; ls -l afile
-rwxr--r-- 1 jackman jackman 0 Aug 21 11:23 afile*
$ chmod u=x afile; ls -l afile
---xr--r-- 1 jackman jackman 0 Aug 21 11:23 afile*