I grepped for clinic in the source code and I have a hunch why this confusing: each clinic-generated block has *three* marker comments, each containing [clinic] or [clinic checksum: ...].

TBH I can't always tell on which side of the comment the generated code sits, so I agree it would be nice if there was an additional keyword clearly indicating begin/end.

Looking more carefully it seems the pattern is

/*[clinic]
.
. (this seems to be the clinic input)
.
[clinic]*/
.
. (this seems to be generated)
.
/*[clinic checksum: da39a3ee5e6b4b0d3255bfef95601890afd80709]*/

I expect things would be clearer to the uninitiated if instead they said something like:

/*[clinic input]
.
.
.
[clinic start generated code]*/
.
.
.
/*[clinic end generated code; checksum: da39a3ee5e6b4b0d3255bfef95601890afd80709]*/

Larry, would that be easy?