The key thing to remember is that the marker stores information about how the model is drawn when the marker is placed: color, texture, scale, orientation, what tool was used, etc. It does NOT store geometry.
While you are in Edit Mode, you can sculpt detail on the model using the sculpting tool. However, switching in the Tool palette to anything other than the model that you are working will immediately convert the model to pixols. At that point, it is no longer editable as polygons.
What the marker does is allow you to easily redraw the model as it was at the time that the marker was placed. It will not incorporate anything that you have done to the model with the 2.5D tools into the geometry.
TextureMaster does indeed give you more options. Using it, you can drop the model to the canvas at a particular angle, paint whatever detail you want onto it using any of ZBrush’s tools, and then pick the model up from the canvas again. Whatever you have painted will be transferred onto the texture of the model beneath. TextureMaster handles the process of unwrapping you work so that you don’t need to worry about compensating for seams or distortions. When using TextureMaster, you do not even need to think about markers.
Regarding Dave Cardwell’s troll, it is important to bear in mind that he is using the beta version of ZBrush. It incorporates displacement mapping and high mesh resolution features that are not available in ZBrush 1.55b. In short, he is giving a preview of some of the things that will be possible when the new version is released and it is unlikely that you will be able to duplicate those particular results in the current version.
Just to let you know, the new version will be a free upgrade to all registered users of the current version. This means that you could purchase the current version to begin taking advantage of ZSphere sculpting and TextureMaster, then receive the hi-res and displacement features when the new version is released. In fact, there is a big advantage to this in that there would then be less for you to learn when the new version comes out, and you could dive into the new features much more quickly than if you wait and try to learn everything at once.