(1) Has there ever been a comet bright enough to be seen
in daylight?

ANSWER: Yes! ...In 44 B.C., just months after the assassination
of Julius Caesar, a comet [nuclei] was seen in daylight by Romans
during the summer months of that year....Julius Caesar's nephew, Augustus
commemorated that rare astronomy event in 18 B.C., by minting a coin.
Astronomers say that that comet nuclei must have been as bright
as "-7 Magnitude"...Venus [usually] gets to about -4 Magnitude i brightness by comparison.

(2) Has Venus ever been bright enough to see in daylight [twilight excluded]?

ANSWER: Yes!....During the era of Napolean Bonaparte, Venus was observed in broad daylight. The circumstances are unknown as to why this was so....My theory is that a combination of localized high-clouds obscuring the sun, and perhaps a brightening of the actual cloud tops
of Venus occurred [Volcanic eruption? asteroid impact?]...