I'm not a person with a minority Sexual Orientation/Gender Identity, but here are my two cents: I think upvoting supportive content in a space that's safe and welcoming to people with minority SOGIs is zero impact, online commenting in that same welcoming space is about as impactful as upvoting in a less welcoming space, both of which are directly adjacent to zero impact. I reckon that negatively reacting to an SOGI antagonist (eg the coworker you mentioned), is an appreciable act of allyship, more impact than a token gesture during Pride. I'm not sure if it would be higher or lower than an anonymous complaint to HR about discriminatory language.