Not everyone has a LinkedIn account, not everyone may know that “Naomi” is usually feminine, and the article run through a textual gender analyser does read as “masculine”.

Mis-stating gender might be careless when as you imply “their” is the always the safe bet, but it’s probably not enough to justify OP’s unduly critical response. He / she or they could have just replied with “I checked their LinkedIn and Naomi’s a girl, btw”.