But this to use bbCode in a forum like this. It also depends on the installation of the forum and the modifications done. In this forum, as example, you don’t need to use the BBCode tags to parse the url, it is done automatically. Of course, each forum has its own set of tips and tricks to deal with spam and there may be a scripts that will disable the link whether you use BBCode or not.
We use some of those scripts to flag suspicious posts which depending on the level of danger may be automatically moderated so people will not see. Some scripts disable the links and leave them as text.