yeah, I always forget that there are endusers working with this
But of course it would be important for them to know, that no changes are applied. And to inform the admin, they should have a way to copy&paste the relevant error from httpd -t. Currently even I can't see the error in the log, I have to copy the "broken" config there, run httpd -t manually and check the error.
Thinking about bigger sites, where users can (can they?) enter Apache directives, they could break the system for everyone else...
Just a thought, I'm the only user of ISPconfig here, and *I* know now about the importance of checking that log