Using medical or psychiatric diagnosis terms when they're not warranted.

Being detail-oriented (in and of itself) is not OCD.

Feeling restless or bored or impatient (in and of themselves) is not ADHD.

Feeling social different or awkward or uncomfortable (again....) is not ASD or "autism"

People throw around these words (e.g. "Oh, that picture wasn't hanging straight and I needed to fix it once I noticed. I'm so OCD.") very casually or self-diagnose, often based on one feature of condition, which greatly devalues the proper use of the terms.