[pcarmichael]

That got me intrigued too. Found a bit more info on it in the comments of a reddit post here: https://www.reddit.com/r/space/comments/3xtu76/comet_lander_...

[mikeash]

Thanks. This seems to be the key relevant quote from that thread: "The RSSI telemetry showed a single value sticking out of the noise, that's it."

So, just something random. Computer glitch, cosmic ray whacking something, or similar. Not aliens, alas.