I have one doubt that I hope I'll solve once and for all after this inquiry...
(1) Can Foolish Words be revealed as an on-guard card played on a company where a character, which tries to make an influence attempt, was played in site phase through We Have Come to Kill or A Chance Meeting?
Rules Erratum: An on-guard card may only be revealed if it could have also been played during the movement/hazard phase. This means all targets of the card must have existed during the movement/hazard phase in order for the card to be revealed.
If I strictly follow the Rules Erratum, it seems that Foolish Words can't target that character... but reading Foolish Words card text I may understand that "card text overrides rules" and no need that character was a valid target during movement/hazard phase...Foolish Words:
Any riddling roll, offering attempt, or influence attempt by the target character is modified by -4. If placed on-guard, it may be revealed and played when a character in the company declares a riddling, offering, or influence attempt.
During his organization phase, a character with this card may tap to attempt to remove it. Make a roll (or draw a #): if this result is greater than 7, discard this card.
(2) And what if the character was in the company during m/h phase, is sent to the player's hand (eg: Call of Home) and played again in sites phase?
This scenario, in an online tournament some years ago, in a game between Brian Min and Manuel Cabezalí, was "ruled" that on-guard Foolish Word's couldn't target the bouncing character.
(3) And something slightly different... what if the character was in the company during m/h phase with a Foolish Words on it, the player plays Voices of Malice / Marvels Told on that card... can a Foolish Words on guard target this character which hasn't been a valid objective during "some time" in m/h phase because Foolish Words can't be duplicated?