Thanks for feedback. I am glad u liked how theme looks.
I agree with you, it is a bit overkill to use a jquery for that purpose including a setInterval function. But, the problem begins with the js script executing only once, as clicking on discussion for example, or header, won't load whole page, but just #app id etc, so script won't be executed again which means it won't work as it is supposed (talking about header hiding on discussions, and reappear on index page).
As well, that's the only way i could think of for header to be changeable, based on, if user is guest or registered or to hide elements on some pages, without touching a core and to keep a easy process of installation for end users.
Thanks for advice about jquery (i planned for script to be a little bit different) so i probably forgot to delete src, i appreciate it.
Again, thank you for feedback.