I’ve been hearing this from the old and young salts, the young probably get it from the old, since me sailing days in the GOM, SW FL— > 30 yr past. Is it because at night it’s likely to be more difficult to reef due to dim light, or b/c of the darkness one might not be able to foresee conditions, or something other? Back in the day when you had to go to the mast to reef, darkness could be a factor. Now, with in-cockpit reefing systems, why as a matter of routine sailing be reefed at night, etc? I still wonder.

Seems more a matter of sailing lore than actual seamanship.