Thanks for your interest!
Erosion is indeed just constant weathering at the moment, the idea being that at the timescale (~200,000 years per step) and cell size (~1000 km²) that I’m working at slope is a close enough proxy to various forms of water erosion. Sediment deposition will occur at rough river deltas once I fix it. I have yet to look into deposition further up stream.
The marching mountains do create some quite interesting features, but I do plan to fix them as I expect they will cause some undesired and hard to track down effects as I make the model more complex.
Is the model you are working on the same one from your two articles? Your approach to lake and river finding looks quite nifty! I’ll have to read over them again in the morning.