Just to clarify on the "knockoffs", it can occur in vanilla as well (but is much more difficult). This is exactly what needs to happen.

1) There is a resource that you have previously uncovered but no longer have line of sight to (you can see it on the map but its grayed out).

2) You have a merchant that can reach that resource in a single turn from his current position, even though it is currently under fog of war.

3) You click for the merchant to move onto the resource directly. He walks over to the resource, and it is revealed (along with the fact that there is a merchant on it).

4) However, the merchant will still walk onto the resource and displace the hostile merchant one square away. This is the same behavior always seen with agents because they don't assert a zone of control (you see this when you walk your diplomats past other diplomats, for instance). It just has an unintended effect in this case because its easier to defend against an acquistion than make one.

So... as you can imagine, this situation is just much more common in PF because merchants can more easily outrun their LOS in a single tun.

Hope this helps clarify.

Thanks,
S