Compatibility shims are our way of telling MaxTo that some programs react badly to being handled by some of MaxTo's functionality.
Each compatibility shim has a description text and a list of functionality that is affected. Some are small and do not result in loss of functionality, others cause MaxTo not to work at all (and the reason for the compatibility shim then is simply to prevent apps from crashing).
This list is kept up to date outside of MaxTo's release cycle, and will be updated automatically by MaxTo.