I was recently browsing my copy of ACKS, and I noticed this passage about the impact of charisma on reaction rolls (page 99):
In cases where the reaction of the monsters to the party is not obvious, a reaction roll may be made. The Judge rolls 2d6, adding the Charisma bonus of the “lead” character (or applying his Charisma penalty) along with any other adjustments he feels are reasonable, and consults the Monster Reaction table below…
This is, of course, just the standard 2d6 D&D reaction roll (the best social mechanic in the history of RPGs). The part that stood out for me was the application of the lead character’s charisma to the check. For games with a Moldvay style ability score modifier, this would lead to an interesting trade-off, as the character with the highest charisma is unlikely to be the best frontline fighter. Do you want to expose a potentially more vulnerable character to frontal assaults in return for a greater chance at indifferent and friendly reactions? Trade-offs like this are what make the game interesting to me.
For comparison, here is how the D&D Rules Cyclopedia handles charisma and encounter reaction rolls (page 93):
After the first round, the DM should modify the 2d6 roll of the character talking for the group by the character’s Charisma bonuses or penalties. For the first reaction roll, the DM shouldn’t take Charisma adjustments into account.
So I think this “lead character charisma” thing is an ACKS innovation (please correct me if you know otherwise). Moldvay does not include any mention of charisma in his section MONSTER ACTIONS (page B24), though his section on charisma (page B7) does mention the applicability of charisma to talking with monsters (implicitly, this seems to agree with the RC version, that the initial reaction should not be modified by charisma):
The adjustment to reactions may help or hinder “first impressions” when talking to an encountered creature or person (see Monster Reactions, page B24, and NPC Reactions, page B21).
It’s interesting how many variations on this there are, even just within the original and basic D&D traditions. OD&D, for example, does not list charisma as something that should affect random actions by monsters. See The Underworld & Wilderness Adventures, page 12:
The dice score is to be modified by additions and subtractions for such things as bribes offered, fear, alignment of the parties concerned, etc.
As expected, the OD&D version plays down character attributes in favor of player skill and strategies.
For me, the ACKS passage brings to mind images of monsters slithering in the darkness of the underworld, but still fascinated by the otherworldly beauty or presence of some character like a bard, paladin, or elf. For some reason I find this compelling. It’s an interesting idea, though if followed strictly it might lead to characters with leaders that have 18 charisma (+3 in ACKS) never being attacked immediately by creatures that use the reaction table (some creatures, like undead and mortal enemies, are of course a special matter).