I don't believe there is any kind of specific policy against that. Probably the thing that I see most commonly sold in that manner is Duskruin entries. Those are sold in mass quantities for silvers from one player to another.
When the elans (for property changes) were out, I bought a bunch. Then when I re-read the actual property page, I realized I had over-bought... so I sold several sets to folks who needed some but the window had closed.