Sharing Trees.

[Raldo]

Unless this changed since after 1.18 (I doubt it has), one player's gathering has no effect on another player's gathering in terms of success rates, number of attempts, etc. The only way you can affect another player is if you trigger the 'The Tree has been exhausted' (or whatever it says), and the gathering point despawns; in that case, the other gatherer will be forced to abort the remainder of their gathering attempts at that gathering point, but this is certainly no reason to get upset that someone is logging alongside you (unless they're way under-ranked for the gathering grade and are following you around to find trees, frequently triggering the 'tree has been exhausted' message).

Your situation sounds fine, unless you're doing that last thing I mentioned. You're probably just logging alongside someone who should be playing a single-player game; heaven forbid he see someone else doing the same thing as he is.