A person who is painfully average would rate on a scale of 1-10 directly in the middle, a 5. This causes the person to become almost invisible because of their mediocrity rendering them completely undesirable. Therefore it's better to be a 4 than a 5.
I'd rather be with Rachel than Amy. Rachel's a 4 but it's better than being with a painfully average 5.
Someone who does not realize they are being hit on by someone of the same gender. This person may seem to be attracted to someone of their same gender because of their unintentional flirtiness. However, the straight aura exudes from them in waves.
Example 1:
Linda: Cheryl, it is obvious she was trying to get with you.
Cheryl: No she wasn't. She was just being really nice.
Linda: You know you are so painfully straight.
Example 2:
Jake: Bro, you were hardcore flirting with him.
Luke: No I wasn't. I was just making conversation.
Jake: Well it seemed might more than that. The guy was legit getting lusty eyes for you.