Apache cannot handle multiple Listen directives on the same port gracefully. Intentionally create a misconfiguration with multiple Listen directives for the same port, port 80. At startup, apache complains with (98)Address already in use: make_sock: could not bind to address 0.0.0.0:80 and fails to launch. What has happened is that Apache bound to temporarily to the port specified by the first Listen directive then tried to bind to it again as it read the second Listen directive and failed. Ask yourself how much time and effort it would take to track this misconfiguration down based on this erroneous error message. Ideally, Apache should detect the second and subsequent Listen directives on the same port for the same virtual host and report something like "Listen directive conflict: Check Your Configuration". This would save a lot of sleuthing should such a misconfiguration occur.
We could issue a warning when bind addresses are equal, this would catch listen directives such as "localhost:80", "127.0.0.1:80". The warning would be something like: "Multiple Listen directivespoint to the same address".
This isn't a bug but rather an enhancement request. Please reopen when you have a patch that adds this feature.
You're telling us that you intended for apache to fail to launch altogether just because the config contains an extra Listen directive? And you're also telling us that all enhancement requests must be fulfilled a priori, that they can't be filed otherwise or only filed as invalid bugs?