When I read the page I couldn't tell if it was serious or some sort of April Fool's joke that someone forgot to take down and almost immediately dismissed it as something that people would actually use.
The tone of the project itself is similar to the tone of the site, so if you find it off-putting or believe your co-workers would find it unprofessional, the product may not be a great fit for your environment anyway.
We also haven't heard feedback about anyone having difficulty convincing others to try Phabricator because of the project's tone. Again, it's possible we're just not aware of it, but we have heard feedback about other issues in this vein (for example, the LAMP stack being a hard sell).
We use it every day at work. At first we were like, what is this 'Clowncopterize' button? But then we enabled the serious business flag and we were off and running.
We also just got rid of "Clowncopterize":