The syntax of ἐρχόμενον in 1:9

ἦν τὸ φῶς τὸ ἀληθινὸν ὃ φωτίζει πάντα ἄνθρωπον ἐρχόμενον εἰς τὸν κόσμον.

Says ἐρχόμενον (erchomenon, "coming") is a present participle. Its form can be masculine accusative singular or neuter nominative or accusative singular, so the grammar allows two attachments:

1. With ἄνθρωπον (masculine accusative): "...which gives light to every person coming into the world" (KJV). In favor: the participle sits right next to ἄνθρωπον. Against: the phrase is redundant after πάντα.
2. With τὸ φῶς (neuter nominative), either as a periphrastic imperfect ἦν … ἐρχόμενον ("the true light … was coming into the world") or as a predicate ("the true light … was the one coming"). BSB takes it this way. In favor: John repeatedly uses "come into the world" for Christ and for the light (3:19; 6:14; 11:27; 12:46), and 1:10–11 go on to narrate that coming. Against: ἦν is far from the participle for a periphrastic.

Says ὃ φωτίζει: the neuter relative ὃ refers to τὸ φῶς. φωτίζω (phōtizō) means "give light to, illuminate."

Implies The light's reach is universal ("every person"). The verb does not say that every person is saved, because 1:10–11 record rejection.

Uncertain Which attachment John intended. The team slightly prefers option 2, which matches BSB and Johannine usage.