While testing I saw "co-founded" flagged, and assumed DisjointPrefixes would suggest changing it to "cofounded", but it made a seemingly bizarre suggestion instead:

The text "In 2014, he co-founded Social Chain" got flagged with "The form of the verb must agree in grammatical number with the pronoun." It wants to change "co" to "cos".

I assumed a quirk of the dictionary having "co" marked as a verb. But it's marked as co/~NSI(dE with no /V to signify "verb"

But /I does signify "pronoun". I know there's been new pronouns invented but this is not one that I've heard before. It's in Wiktionary:

co (third-person singular, gender-neutral, reflexive coself)

(nonstandard) Gender-neutral subject pronoun, coordinate with gendered pronouns he and she.
(nonstandard) Gender-neutral object pronoun, coordinate with gendered pronouns him and her.

So we could just remove this annotation, but the question is why does it change "co" to "cos"? You don't normally add an "s" to pluralize pronouns in English like you do for regular nouns or to make the 3rd person singular present form of a verb.

I think there's some broken logic revealed here that needs to be investigated for a proper fix.