@Evgura It's normal Readmore button with boostrap class. And it's not spoiler, it's summary of page, so shortcodes are used.
But if you need it in forum posts with link created with bbcode link, you can use style bbcode-link class. Unfortunately you can't send class as parameter with bbcode link. But you can use span tags around it and then you could have different styles. If you point me to exact example what you need, I could try it (one link, all links, what colour etc)