What is a word that defines a person who adds to a topic or conversation needlessly?

Boorish

^Boorish is good. Fool? That might apply as well.

A digresser.

I don’t think there is a specific noun for that.

Buttinsky? rofl

A horner.

Derailer or Sidetracker

Redunder.
Trumpetist.

The only way to respond to such a person is with a blank, unresponsive stare that says, “What the eff are you saying?”

A commenter from the peanut gallery.
or…
Divergent opinionator?
A victim of over-moderation?

There is no general word for it. A “heckler” seems like a reasonable one-word fit, sort of. Or a smarty-Alec, smartypants, or wise-ass.

Context and perspective are important. One person might call them hilarious, another annoying or offensive, and/or call them a troll, and another person seeing the same comment might think it is the most appropriate response.

Thank you everyone. I believe it’s something along the lines of someone who always has to have the final word, wants to always be right, and one-ups the next.

Like a conversational usurper?

@Parmenides Oh, I get it now – you mean a man! :-)

Now not any man has balls big enough to reply to you, @janbb….

@janbb that may unfortunately, be the best answer. I guess there isn’t a word for it yet.

@Parmenides Yup. As I said in my first response, I don’t think there is a single word for it.

An outtalker. Or an ultimumbler