Short answer; really difficult/no in most cases.

If the razor is new, with an untouched rounded spine and the edge is beautifully sharp, then tape was used. Or if there is a difference between the polishing degree of the spine and the edge, although not a reliable method.
The "hollower" the grind of the razor, the harder it is to see if tape was used; on a wedge razor you can see it if you try. There are also the secondary bevels, where you see an angle forming on the edge, and a millimeter or less behind it, although it disappears soon. That's also a sign that tape was used.
I use tape almost always, the razor keeps its mint-like appearance and lasts longer since less steel is removed (not that it won't outlive if you are a bit careful with it). I also think that, a lot of new users have a problem with rehoning (or stropping a razor on a paddle strop, that's kind of serious) a razor, honed by the previous owner using tape, so for my case I always mention it, either on my ad or on mails and ask if he wants me to return it back to how it was without tape.
As for the "the angle has a meaning", that's a lie; I've shaved with a close to 90 degree edge. You can do some crazy stuff with a 90 degree edge, just don't let your guard down.