HaLeiVi-
I’m not sure you can say that once you put it on Bihetter you may keep it on, since we find by Kohanim that they must remove it after the Avoda, because of the Klayim.
I was thinking of this, but ?”? in the Rambam in Hil. Klei Mikdash (Perek 8) where he doesn’t say they have to take it off, so it all works out ??????.
Here too, perhaps it is Muttar to keep it on into the night for the amount of time that people normally wear day clothes at night.
You’re mixing up the two shitos. I was asking on the Rambam who holds it’s not dependent on day clothes or night clothes but rather on time.
As for your Stira in Rashi, the Bach has an approach that explains Rashi to hold that it goes by the Begged. Where he says, he might put it on at night, it means, he might use it as a night garment.
Thanks:)