Just in case it is possible to clarify - Antipodes/K9s have Sensor and the camouflaged state. Does the Sensor zone operate, preventing enemies from re-Camouflaging, while the Antipode is still camouflaged? Ie - can a marker use the passive Sensor effect or only a Trooper represented by a model?
Generally speaking, you have to reveal in order to "prove" that you have the skill - classic example is if you want to use the repeater on a camouflaged model.
If that is the case... a K9 could simply ARO with change of face, revealing itself, and thereby waste the long skill the enemy declared for re-camoing?
That's specifically called out in the Repeater rules. "Repeater + Impersonation or Camouflage and Hiding Troopers or pieces of Equipment that have Repeater in addition to any Special Skills that allows them to act as Markers instead of figures (Camouflage and Hiding, Impersonation...) reveal themselves automatically if a friendly Hackerattempts to use their Repeater ability. Hackers cannot use a repeater carried by an enemy trooper in a Marker state. Repeater and Hidden Deployment Troopers with Repeater who are using Hidden Deployment reveal themselves automatically if a friendly Hacker attempts to use their Repeater ability." Sensor does not contain the same provisions. OTOH Sensor does say: " Enemies with the CH: Camouflage or CH: TO CamouflageSpecial Skills cannot regain the Camouflaged or TO Camouflaged state inside the Zone of Control of a trooper with the Sensor Special Skill." An Antipodes that is a marker may not qualify for this provision. However, Camouflage and Hiding treats Camouflaged mines/other markers as troopers for the purposes of preventing recamoing. So it's not consistent as to whether a marker would count for the purposes of triggering Sensor's rules. Tl:dr I don't know. From a purely gameplay POV, I think that it's better that the Antipode needs to be revealed. This is not an issue as the Entire Order to Recamo will trigger a ZOC ARO that the Antipode can use to to reveal themselves and prevent the enemy recamoing.
Thinking about this some more. The position I prefer from a gameplay POV (Sensor only works for troopers represented by a model not markers) is the RAWest interpretation. So absent someone saying "yeah nah, actually the get it even while in a Marker state" I'd suggest playing it that way
We already know from other rules interactions that the K-9 will not cease being troopers just because they are in Marker state. I can only surmise that this is an interaction that hasn't come up before. RAWest atm is that you simply have to point out that a Camo has Sensor if it is relevant and that this causes the recamo order to fail.
Why should you have to reveal? Have you to reveal a camo marker when you won't to place it outside your deployment zone? In Infinity you have to trust your oponent in some situtaions. And imo you can't recamo in the ZOC of an Antipode in camo state. EDIT: And repeater doesn't work the same way, cause Sensor is passiv and repeater are active in use.
There is nothing in the rules saying you have to de-camo (you are not performing any action) so you don't have to Regarding the "trust" issue : all 40mm marker in Ariadna have sensor so there is no trust issue Versus Pano who now have the Zulu Cobra with Sensor, I imagine you may ask the referee to check