Well, we are getting further ahead. Can you post some pictures of the leak please?
If it is a cylinder head gasket leak, it may be either because the seal around the combustion chamber has blown, or because the oil passage to the valve gear is leaking. It is important to know which, and pictures may tell us, particularly if you clean the area, then make it leak and photograph it immediately.
I customarily address these problems in the Sherlock Holmes manner, by tracing cause to effect. If the cause were over-filling with oil, I do not think it all that likely that the result would be a blown-out top crankshaft seal: in my experience those seals are not all that easily pushed out, while some of the engine gaskets are relatively easily blown. I have seen this problem before, though on a copy of a Honda not a real one (the copies are called "chondas" here in honour of their country of origin) and the symptoms so far are reasonably similar - however oil came out through a multitude of gaskets on that engine, not from under the engine's red plastic top cover, as it would if the top crankshaft seal were leaking. My first guess would be that the excess oil that was in your Honda has caused oil to flood through the PCV valve into the oil-separating compartment under the flywheel, and (probably temporarily) caused the valve to stop working, thus pressurising the crankcase and forcing oil out from the point of least resistance. If it couldn't go through the PCV valve, it had to blow a gasket or a seal. In that other case, the oil began by coming out past the gasket around the cylinder head's valve gear oil passage (underneath the head, not on top of it), but as the mower kept being run, it started coming out from the crankcase cover and the bottom oil seal as well. You can help resolve this possibility with your engine, by pulling off the rubber breather hose from the bottom of the air cleaner box and seeing if there is oil in the hose. If there is, it is consistent with my guess, though it does not confirm it. Incidentally, please do not run the engine for long, since if it is generating pressure in the crankcase, it may blow a gasket rather than cause one to leak temporarily. This is more difficult to fix.
