Speaking as a groundlubber, it strikes me that after a hard touchdown and go-around, I would not trust the gear to come up and then go back down and lock again because of possible damage.
It would seem my best bet would be to leave them down if the plane were flyable with them down and not risk the possibility of damage preventing them from coming down and locking again, as I think French G. noted as Naval practice.
Those <ahem> chemtrails off the outboard flaps or aelerons seem to be fairly common in the bunch of aeronautical vids I've watched. Seems like the air gets compressed in front of the flaps or aelerons, then as it slides off the outside end, the pressure suddenly drops below the dew point, causing the trailing cloud formation out there.
Now y' unnerstand, I are not a pilot nor uh aireonautikel engineer, so I'm not even clear on what's a flap versus an aeleron, but I've seen a lot of videos where that cloud trail off those surfaces occurs in planes landing. And it's not off the wingtips (although that can happen too), it's off the outboard edges of the flaps/aelerons.
I think it's more of a question of local atmospheric conditions than altitude per se.
I think.
Groundlubber Terry, watcher of many plane videos from his cushy living room couch. <Not to be construed as a "qualification," 230RN