eirk in safari, you can drag a normal tab to the other pinned tabs (there needs to be at least on there already) to pin it, or drag a pinned tab out of the pinned tab area to make it a normal one. also, you can reorder pinned tabs.
Vlad eirk Orion iOS doesnt have pinned tabs to begin with (I think there is an issue for that can you find so we can merge this)