Hi @infernoprime,
Topics are not blog posts, they can be attached to only one forum/category. There is no way to show the same topic in multiple forums, this is out of the forum logic. I have no idea where and in which forum platform you have seen such things. It could be an extension, but it cannot be a built-in feature, or you’re talking about very rare forums oftwares.
In any case we’re sorry, but we don’t consider adding such feature, instead you can add an information box on the top of the forum with a link to the “posting guide” topic. Just navigate to Dashboard > Forums > Tools > Misc Tab and create the information box which will be displayed for certain usergroups on certain forum pages.