I'd agree in general, but why think that the Arcan dev doesn't understand Unix? There's nothing in the Unix philosophy that says we have to wed ourselves to the specific weirdnesses of old DEC terminals forever.

> Confusion between user-input and data – programs can’t reliably distinguish between interactive (keyboard) input, pasted/”IPC” input and other forms of data entry.

No! This is a feature. The actual core data-processing part of a program should not care where its data comes from. There needs to be separation between engine and interface, and different interfaces are needed for different types of input scenarios.