Solemnity is a truly underrated card (in Commander, I mean). It's great and works in a lot of combos, I love it! My favorites it's Solemnity + Decree of Silence, Priceless! :D
Solemnity and naked singularity are the perfect combo of confusion and persistence, at least after a couple of turns you generally sac the singularity, but with solemnity you don't have to, and that's scary... I would love to play this combo in my commander group
Print em off the gatherer rule page. You put the counter on and then pay the cost for each counter. If you can't put a counter on, then you pay the cost for zero counters...which is zero. If there are counters already on the remora, you still need to, but it will be a flat cost for the rest of the game.