At this moment, almost 10.000 plugins are offered on WordPress.org Many of these are very usable and of good quality. However, according to 'industry standards' or 'common practises' for most programming languages, automated reports are generated on code style and quality.
For WordPress itself and all of its plugins and themes, automatically some code style and quality reports should be made available.
To name just a few which are very common to use with PHP are:
1) PHP Codesniffer (coding standards)
$ phpcs plugin/xyz > /tmp/xyz-phpcs.txt
2) PHP MD (mess detector, code quality)
$ php -d memory_limit=128M /tools/phpmd/phpmd.php plugin/xyz html codesize --reportfile /tmp/xyz-phpmd.html
3) PHP Depend (code metrics, code quality)
$ /tools/PHP_Depend/pdepend.php -d memory_limit=128M --bad-documentation --summary-xml=/tmp/xyz-pdepend-summary.xml --phpunit-xml=/tmp/xyz-pdepend-phpunit.xml --jdepend-chart=/tmp/xyz-pdepend-jdepend.svg --overview-pyramid=/tmp/xyz-pdepend-pyramid.svg plugin/xyz
Output files from here van be converted like this:
inkscape -z --file=file.svg --export-png=file.svg
and converted to a smaller format with:
convert file.png file.jpg
All results from these tests should be made available in the plugin page on WordPress.org for each of version of the plugin.
Note: it is not to force everyone to work according to certain schemes, but is has been proven over many different computer languages and software projects, that this kind of reporting as a standard part of the development cycle is promoting quality.
These results are never absolute numbers, hence it is not possible to rate an plugin 'A' of 10-out-of-10. However, for small plugins that only sport a simple widget, it should be possible to pass all tests without any warning or errors.
Offering this information will help the user in selecting which plugin would be the least of concers, since style and quality is way better compared to other plugins. This would provide an indication that such a plugin would be easier to maintain/migrate/debug/extend/etc.
For the developers, it would be feedback, that the software offered is has room for improvement. Especially on all the items reported. Of course not all can be always fixed and 1000 people have 1000 different ways of code styles.
Simply offering this information would reveal with how much skill the code has been put together and motivate to improve or at least maintain that level of quality.
Implementing such quality reports for WordPress, its plugins and its themes would give the overall quality of WordPress a boost for improving coding style and code quality to prevent bugs and make maintenance and further development easier.
When such a system is in place, WordPress could display a quality approval icon for each plugin that meets certain standards. In order to make the implementation successful, I would like to suggest to implement it step by step.