Danbooru uses an awkward way of linking. Put the words you want to appear in full quotes, then a colon, then the URL with no spaces. 'Such as this one':http://danbooru.me/post/show/726274 with quotes instead of apostrophes would link. Alternatively, posts on Danbooru and its mirrors will autolink when you plainly type, for example, post #726274. The benefit being clickers will stay on their domain instead of being transferred to the one you use.