Bootstrap and forums should not be mentioned in same sentence... or same post... or thread or even website. Bootstrap is excellent for basic website pages, but it is completely useless for forum style and should be avoided like plague.
In Bootstrap classes set predefined behavior. To change behavior all you have to do is change class name of element. That is completely opposite of what forum styles should do: HTML should set semantic structure, CSS should define behavior. In order to change forum style author or forum owner should simply edit CSS. That is not how Bootstrap or any other framework works.
Frameworks like that are good only for simple websites created by people with no time or experience creating proper websites.