Kashakunaki's page

Grammatically speaking it absolutely is incorrect and unclear. The community has just mostly agreed upon that interpretation, and that was not what I recommended it read. Something like "light piercing melee and one-handed piercing melee weapons" would clear everything up.

You're saying two is the correct interpretation with no evidence to support it. I don't doubt that that was the intention of the ability, but as it is it isn't clear. There absolutely is need for an errata. If about 20% of the community is unclear on it then it has been poorly done and those that are convinced in their beliefs, like yourself, have no hard evidence to support yourselves.

Swashbuckler Finesse, the weapons usable to increase panache with killing or critical blows, as well as other items in the Swashbuckler class breakdown are grammatically fuzzy at best.

I've heard many different opinions with varying amounts of support to back up their beliefs on reddit subreddits and else where, but I want a Paizo official ruling on the matter.

"...gains the benefits of the Weapon Finesse feat with light or one-handed piercing melee weapons...."

Grammatically, the implication is light melee weapons and one-handed piercing melee weapons.

However, a fair amount of people argue the intention is light piercing melee weapons and one-handed piercing melee weapons.

Could Paizo please clarify.

A piece that user mjmeans posted to help illustrate my point:
"So, 'with light or one-handed piercing melee weapons'. Without the oxford comma, this sentence fragment is unclear. Light and one-handed are exclusive groups, but piercing and melee are not. Does the benefit apply to:

1) all 'light weapons' AND all 'one-handed piecing melee weapons' i.e. 'light weapons or one-handed piercing melee weapons'

2) all 'light piercing melee weapons' AND all 'one-handed piercing melee weapons' i.e. 'piercing melee weapons, that are either light or one-handed'

3) all 'light melee weapons' AND all 'one-handed piercing melee weapons' i.e. 'melee weapons, that are either light or one-handed piercing'

The strict English reading, because there are no commas in this sentence fragment, is number 1 above."