Don't hate your builders and themers
If you are a Drupal module developer, I have a request for you. A plea for you to help make my life easier, and likely the lives of many other site builders.
I'm currently building a website that uses a theme override to display a prettily formatted username. Drupal provides a way to do this via the theme_username() API call, so in all places where Drupal core displays a user's name, my pretty string now shows.
However, when I started adding contrib modules for extra functionality, I found that quite a few of these don't use the theme call to display a user's name. Instead, they simply print out the value of the name field in the user object. If I want to change that as a site builder, my only choice is to hack up the module so it displays what I need.
For example, a Drupal 6 module might set a page title on a tab somewhere in the user account like this:
drupal_set_title(t('Widgets for !username', array('!username' => $account->name)));
Whilst what it should be doing is passing the name through the theme layer first, like this:
drupal_set_title(t('Widgets for @username', array('@username' => strip_tags(theme('username', $account)))));
And the same goes for calls to drupal_set_message() for status or error notifications, or anywhere else a user's name might be displayed.
This way the site builder is in charge of how users are displayed and won't need to hack up any contrib modules. Though that's not hard, it makes updating them unnecessarily painful, as any changes would need to be re-applied.
So my plea is, if you're a module developer and your module displays $account->name somewhere, please change your module to use theme('username') instead.
Conversely, if you're using a contrib module and find that it prints $account->name when it really should use theme('username'), please open an issue and attach a patch if you can. I will :-)