"That's certainly a thing" refers to phrases such as "You definitely said words." It expresses that one wants to acknowledge that something happened which demands commentary, but the commentary is self-evident, and thus sarcastically skipped.
"That's certainly a thing" refers to phrases such as "You definitely said words." It expresses that one wants to acknowledge that something happened which demands commentary, but the commentary is self-evident, and thus sarcastically skipped.