The quote below is snipped from the second link, which in itself references another, older long thread:
snailish said: ↑
“The understanding from the long thread that was linked is that charisma has a bunch of "secondary roll" functions outside of the vendor pricing aspect.
-charm/mez break but the math is so negligible with other changes to resist checks or something that no one needs to worry about it -lull success and aggro or not on fail, with a believed threshold of 150ish and 200 for max bonus (no scaling past 200) -memblur success something similar to the lull
Basically meaning a chanter wearing normal chanter gear and using buffs will hit the threshold for charisma's real benefit without purposely stacking cha. As chanter gear is so INT heavy there is also little reason to stack INT. STA helps early on, and STR can as well, as noted in this thread STR is also not a stat that logically stacks on normal chanter itemization.
all of this subject to verification, as it is just a paraphrase of the very long linked thread.”
Note that it was mentioned elsewhere on the official boards that "charisma impacting non-enchanter charming was removed 10 years ago". That would need verification, but does match the anecdotal comments of halfling druids with 50 cha charming without issue.