Whilst the president is talking Mr Biden has made numerous expressions which appear to convey disagreement or bemusement.
One viewer tweeted: “Biden’s smiling and phony facial expressions are really annoying me.”
Author Sarah Pinsker added: “I recommend turning off the sound and just watching Biden’s facial expressions in response.”
The two presidential candidates clashed over Mr Trump’s handling of the coronavirus, ties to foreign powers and healthcare costs.
Both Mr Trump and Mr Biden implied family members of their rival had profited due to their public positions.
Tom Nichols, who supports the anti-Trump conservative group The Lincoln Project, also tweeted about Mr Biden’s facial expressions.
He said: “The moderator is asking about him calling Fauci and the doctors idiots.
“Trump interrupts and begins digging deeper again, Biden‘s facial expression: ‘I can’t believe he’s doing this’.”
More to follow…