If any player happen to remove a tree in multiplayer games, other players can see the trees disappearing etc even when they have no vision over area under question. Fog of war is ignored when it comes to tree removal.

Gameplay wise this bug is more important than it seems to be, especially on maps heavily covered with trees, or gamemodes with special rules (like Nuclear War). On Nuclear War it hints the placements of enemy buildings (in the past players used to bulldoser trees off for some extra building space, so their bases don't get removed with a single shot); on maps like The Abyss it may give away potential attacks.