The suffix for semel files is ".tse" (for "The Semel Editor (TM)").
Semel files are not human-readable.

Did you know that "human-readable" is a retronym?

What's a retronym?
"A retronym is a term consisting of a noun and a modifier which specifies the original meaning of the noun."
Before computers, anything that was "readable" was "human-readable" by definition.