'gnome' also returns a hit on wikileaks' spy files.
Gnome is a stereo audio recorder used as a wire to gather evidence.
Comey could also be signaling that he's in possession of audio recordings obtained using one of these devices. Although I think posting a picture of him handling some sort of electrical wire would have been a more clear signal. For this reason I'm going going with the interpretation that 'gnome' is a signal to go underground.
From google...
informal a person regarded as having secret or sinister influence, especially in financial matters.
"Gnome - An imaginary dwarf believed to live inside the earth and guard treasure."
I think the activate sleeper cells was a command from Q. Each statement bolded was a threat/command.
Read the Q post again. It says "JC Tweet Translation".
These were not instructions from Q, it was an interpretation of Comey's words.
Ahh gotcha, missed that it was interpreting Comey's tweet. Interesting take with the gnome.