I too use Macs and don't seem to have any trouble posting links, here or on other boards I frequent. The html language does not differentiate between originating operating systems. In the case of the link to the New York Times at the start of this thread, the problem is a space before 'html' in the address. The question is, how did the space get there? It could be sloppy typing or it could be an artifact from the Apple Works word processor, if the post was written using that. Apple Works (previously Claris Works) uses some non-standard codes for certain characters which html doesn't recognize. Microsoft Word is even worse for this, which is why you so often see garbled text on the net. The phenomenon even has a name: The Dread Questionmark Disease. I haven't seen Apple Works introduce spaces like this but maybe it has a setting that automatically introduces spaces after periods. That sounds more like a Microsoft-type feature though.

Certainly the problem is not the Mac but more likely the word processor or typist.