Patent 5,946,647 was filed in 1996, when Apple came out with Apple Data Detectors (Mac OS 8). The patent is almost certainly about that.
This article describes ADD, including what its developers considered to be unique and different from other approaches.
My take on this is that ADD did come up with some clever ideas in implementation that solved the particular problems they were addressing (focusing on simple problems and fast detection). It's clear that what's unique is the particular implementation, not the idea of detecting phone numbers and such. They cite lots of other examples of the idea.
So, there are two possibilities. Either the patent covers the idea (and thus is inappropriately broad and will be ruled invalid) or the patent is about the particular implementation, in which case it should be simple to implement in a way that avoids violation. In either case, HTC and Android will be fine.