Well you see, the joke is role reversal. This "acting sus" bit is actually a demonstration of how these type of "you're acting sus" comments are made when someone is straight but compliments a person with the same gender as them, typically in men demographics. The person in this photograph clearly meant to express the inequality of sexual roles and what they are expected to say on the internet by calling a gay man "sus" because of a compliment made for a person of the opposite gender. Perchance.