Does riposte and defensive duelist stack

[Your memes end here]

?

[Recjawjind]

Both use your reaction.

[ComradePreacher]

You can only use one reaction, I would suggest not having defensive duelist if you're using riposte as battle master.

[Hobocop]

Defensive Duelist doesn't use any of your superiority dice, so there's that, even if their function overlaps.

Seems to generally be an overinvestment to have both, though.