Anyone out there ever do, or have done by someone else, a diagnosis of a Coolant Seal failure on a 13B engine (or other rotary for that matter)?

Well, 13Bs have multiple coolant seals so it's hard to say without a teardown...but a diagnosis should be pretty straightforward. Check for signs of coolant leaking out of the engine block, white smoke on cold start (or even worse, while running), a sweet smell to the exhaust, etc. Check your coolant level frequently...if it is repeatedly getting low then you know you have a problem. Also, pull the radiator cap and start the car, let it warm up a bit...look into the radiator...if you see what looks like champagne bubbles in the coolant that's almost a sure sign you've got a bad seal.

What car is this in? Is it stock?

you may also find the coolant pressurizing

Ranger has it right on. I think Limp means excessive pressure.

rebuild time or you can try this http://www.rotaryresurrection.com/3rdgen/tech_coolant_seal_fix.html its only a temporary fix but itll hold of a awhile, did it on my old 7 til i saved up enough money for a TII swap