All good points above.

I'll add that every scratch and nick on all my bikes, I've put there. They're accidental, of course, but there's nothing on any of them that I haven't put there myself. Even out front in the public bike parking racks, (which are right outside a glass wall behind me as I work) I've never seen anyone damaging someone else's bike. I have seen attempted thefts, though. Even the thieves don't want to wreck their target.

I think you may be giving your co-workers less credit than they're due WRT to respecting others' property. Everyone's in the same boat.

That said, I like having a choice of bikes for commuting. I have two dedicated to the task, and my Litespeed makes the trip when I don't have things to tote and the weather cooperates.

Neither of my commuters is an old POS beater. That's key for me. I like what I like, and it's contemporary drivetrains, frames, and carbon forks. I've put a lot of thought and dollars into my rides to make them so that I never feel "less than" on any of them. I'm equally happy commuting on any of the three, even though they're three completely different geometries and two are fully fendered, with rack and dynamo lights.

That may be something to consider as you examine the N+1 question. Why buy something you really don't want to have to ride? Put as much care into the purchase of a commuter that you have into the Domane, and you'll enjoy the ride as much on either bike--even though they're different. Plus, if it's equipped for foul weather, you may find yourself on the bike more often.