Like most of the threads on this forum, the advice there is overly conservative compared to most other sources.
Most such discussions mix up three things:
2) Wear on powertrain components that may lead to early failure.
3) Regulatory weight limits.
For safety, you have to comply with the GAWR on your tow vehicle. For any but the smallest trailers you have to have a WD hitch. You have to have brakes that work properly. You have to have sway control, in almost all cases. You have to be sure that you comply with the GAWR rating on the trailer axles, and also be sure that the individual trailer tires aren't overloaded.
For safety, don't exceed the weight rating on the receiver or any of the hitch components.
In some jurisdictions these safety-related ratings are enforced by law.
The GCWR and towing capacity provided by the vehicle manufacturer are advisory ratings. Exceeding them may lead to premature powertrain wear. Some posters like to derate these capacities by 10%, 15%, 20%, depending on where you are and what kind of engine you have but that's all Kentucky windage around how long the transmission (etc.) will last. Which, if you're going to travel several thousand miles a year or more, may be something you care deeply about. The vehicle manufacturers don't determine these ratings based on safety, and for RVs they have no legal or regulatory significance of any kind in any state in the U.S.
You have to know the actual loaded weight of the trailer to have any idea what's going on. The GVWR on my trailer (10,000) is around 1600 pounds more than the maximum load I've ever been able to put in it even with full tanks. There isn't room for enough cans of baked beans to get it over the max, and it has the optional 2nd air conditioner and some other extras. So while most
trailer manufacturers push the limit, and in many cases ship trailers that are overloaded when empty, not all of them do.
If you're serious about buying a TT but right on the edge for weight then get the dealer to take it over the scales somewhere for you.
There are crashed rigs out there. We've all seen them or at least pictures and video. But it isn't about the weight and it is rare indeed that the weight in and of itself led to the crash. Major causes of loss-of-control crashes:
1) Structural failure of hitch components due to defects or overloading
2) No brakes on trailer. I can't believe how many RVers see brake controllers as optional.
3) No weight distribution or WD bars not properly in place
4) Use of air-ride suspensions on the tow vehicles that adjust ride height.
5) No sway control of any kind or sway bar not tightened.
6) Operation in dangerous winds
7) Catastrophic tire failure
Loss of traction at high speed on ice, snow, or water deep enough to cause hydroplaning
We'd be better served for safety by exhorting all the veteran RVers to pull their hubs every year for a thorough brake inspection and scale the rig every year to make sure the WD is dialed right with even half the determination, energy, and indignation that we expend telling n00bs to buy a bigger truck.