if a post has notes in the thousands, your correction or call-out may not be entirely new to OP and although you’re of course free not to do so, you might spare them some discomfort by checking the notes/their blog to see if discussions are already ongoing.

Imagine that person A has a twin. They try to confuse B by pretending to be the twin. Person B stands close to A, stares at their face for a few seconds, and then turns away, casually remarking they know A isn’t their twin. When A asks how did they know, B reveals that they recognized them by a subtle dimple/small scar on their face that the twin doesn’t have. A is both flattered and flustered that person B noticed this.