This is one, non-autistic person’s thought about functioning labels. For real, in-depth expertise about the matter of functioning labels, please check out the following:
Amy Sequenzia: Attitudes - Grading People
Lydia X.Z. Brown: So High-Functioning (sarcasm)
Kat Williams: The Fallacy of Functioning Labels
Calling someone “high-functioning” in reference to their autism (or other neurodevelopmental disability or difference) is usually not consciously intended to be insulting. It is often said admiringly or appreciatively. But it is actually a particular kind of backhanded compliment.
A backhanded compliment sounds at first and on the surface like a positive remark. But when taken in context, it is clear that the larger, underlying meaning or message is not positive for the recipient. In fact, on examination, it becomes clear that a negative message is being communicated about the larger group the subject belongs to. Whether the speaker intends to do so or not.
“You’re pretty smart for a blonde.” This can be said as a truly playful poke or a painful jab, depending on the intent, but the speaker is very seldom unaware that they are playing around with a common trope about blondes, particularly women. On the surface, the individual has been labeled as smart, but the larger point is that the speaker’s expectations were low, because the group the individual has been tagged as belonging to is considered unintelligent.
“To me, you’re just one of my friends; I don't even think of you as Black!” The compliments floating on the surface here include the fact that the recipient is considered a friend, that the friendship supposedly transcends racial differences, and that the speaker sees the person first and doesn’t categorize them according to race.
The subtext is a reminder that the recipient belongs to a disfavored group and that the speaker is exceptional enough to be friends with them anyway. This is made possible by the fact that their expression of stereotypically Black culture and behavior is muted enough that the non-Black speaker feels comfortable and close with them and can consider them to be a fellow human being. Unlike the larger population of visibly, culturally Black people.
Pointing out how someone is exceptionally superior to the disfavored group they belong to often has the effect of highlighting the low opinion the speaker has of the group as a whole.