If you use sarcasm, you should remain sarcastic throughout. Not be sarcastic for the first sentence and not the second o_o.
Though personally I would've used satire.
"Oh, that is really weird. Especially since mutants can't have photosynthesis, yet you just saw one that did. You even provide support by not giving specific stats for the forest spirit. There are just too many people that try to give mutants stats they can't possibly have. Very nice job going for the impossible ability instead. And to top it off, you smartly avoided adding a screenshot that could have disproved your claim. If we saw a picture in which there was no photosynthetic forest spirit, we might think you were lying or something."