(The above rendering comes from the RJPS translation, an adaptation of the NJPS translation. Before accounting for this rendering, I will analyze the plain sense of the אִישׁ terms, by employing a situation-oriented construal as outlined in “Notes on Gender in Translation,” pp. 11–16.)
In the context of warfare (mentioned at the start of this verse), it would be normal for a specific, newly introduced participant to be labeled in terms of that conflict situation, using the situating noun אִישׁ. (Cf. 1 Kgs 20:20.) Indeed, the qere’s expression אִישׁ מָדוֹן designates a participant whose involvement defines a situation of strife: Jer 15:10; Prov 26:21. I.e., an adversary. Such a construal yields a coherent and informative text here. As Gersonides glossed: רוצה לומר: איש בעל ריב ומלחמה; Targum גְבַר דְמִשְׁחָן = (apparently) “participant who lights a fire.”
As for rendering into English, I have supplemented the NJPS rendering of the kethib by adding an alternative rendering that is based on the qere.