Another angle. It's the inner most leaf. Could it be sun damage of some sort? The plant is indoors and nothing like this has been found on other orchids.
It's hard to say, but to me it doesn't look like a bite. It looks like simple mechanical damage. Maybe the leaf got stuck down in there and got ripped or torn a bit from general movement.
Well, it looks like from how the pot was positioned that perhaps the leaf that was covering it folded up thereby allowing direct sun to beam in to a leaf in its baby stage. I rotated the pot just in case my hypothesis is correct. Anyone else have trouble with sun damage, only on new/baby leaves? The mature leaves on the plant are leathery.
Okay I am blind as a bat, so may want to take with a grain of salt. This looks to me like a mechanical doing. I don't know of any bug that can chew in a straight line :-), and if the plant has been covered with older leaf growth not sure how it could be sun burn. In reading your above post I would think it would be more severe if it were that burned. That looks to me like a more recent cut and heal mark. My paph leaf was cut by me on accident while using a box cutter to cut away all of the newspaper and masking tape. The edges have since dried up and turned brown.