Do solo night time and “towered” landings total separately toward the solo night requirements in FAR 61.129? FAR 61.129(a)(4)(ii) reads as follows for an applicant for commercial airplane single-engine, and makes similar provisions for other categories and classes.

(4) Ten hours of solo flight time … that include -
…
    (ii) 5 hours in night VFR conditions with 10 takeoffs and 10 landings (with each landing involving a flight in the traffic pattern) at an airport with an operating control tower.

Must a solo flight be conducted at night and involve at least one landing at an airport with an operating control tower to count, or do night time and “towered” landings total separately? Given a pilot with five hundred solo night hours all to pilot-controlled airports who goes up at night to fly ten laps around the patch at a nearby Class C, where does that pilot stand with respect to the requirement above?

501 solo night hours and 10 towered landings, or
1 solo night hour and 10 towered landings
Night time does not need to include a landing at a controlled airport to count.  You just must have at least 10 solo night landings at a controlled tower, as well as 10 hours of solo night time, they don't have to happen together (though whatever time it takes you to get those landings counts toward the 10 hours too).

The pilot in your question would have 501 solo night hours and 10 towered landings.