Checked with Miss Nellie who seemed in a surprisingly cheerful mood. No pencil tapping or eyes rolled. Must be early.
No need for an outside confirmation.
For a multi-member team, Pilot A lands and posts "The baton is free." Someone (either Pilot A or Pilot B) checks and confirms that the post is up. Then Pilot B posts "I have the baton." And then he departs.
The trick is to be sure that Pilot A has his post up before Pilot B posts that he has the baton. Because TeamSpeak is likely to be crowded, the safer thing might be for Pilot B, on his own, to confirm Pilot A's post before he makes his own post. It is the team's responsibility to get the sequence right, even if that means waiting a few seconds for the SOH forum to come up.
For a solo entry, all is straightforward. The pilot posts the arrival, watches it come up, and then posts his departure.
Note that the sequence of the posts will be obvious post facto when one looks at the forum thread. (Declaring arrival and departure via forum is a bit clumsy when it would be quicker to use TeamSpeak. The advantage of the forum method is that it leaves an evidentiary trail to assure everyone of proper sequencing.)
Hope this helps.