Whereas I would say that it's only reasonable for the chandelier to not be able to bear the weight of someone is if it's obviously not designed to hold weight or there's a structural deficiency.
If it's the former I haven't described it with enough detail and I'll warn the player. If it's the latter, I've been broadcasting the general state of the building. Whether this particular fixture is on the verge of collapse becomes a judgement call on the side of the player of whether they want to risk it.
On a related note if the player is just adding a feature to the room that's fine, I allow that on a fairly regular basis. But it's still going to follow the same rules. I hadn't thought about there being a chandelier (or any other fixture)? Fine. Who built the structure, what state is it in.
I don't coddle my players. If they want to take a risk, they take the risk. If they're in a building with obvious signs of disrepair and wood rot and they want to swing from the chandelier I shouldn't need to spell out the fact that it may not hold. It should be obvious. If I think it may not be I'll give them an appropriate check.
People do risky things all the time not knowing all possible consequences or even the chance of failure. I see no reason to change that for PCs.
