What this ticket seems to demonstrate, though,
is that the meaning of "-integer" is inconsistent
between [lsort] and [lsearch].  I confirm that.
[lsort] uses Tcl_GetLongFromObj() and [lsearch]
uses Tcl_GetIntFromObj(), so on systems where
int and long are different (64-bit systems),
they are inconsistent.

That's an unfortunate mess.  Whether it's a bug,
and if so whether fixing it would solve more problems
or create more new ones, I'll have to discuss with
others.

This is all a symptom of the messy stew of integer
treatment in Tcl that history has delivered to us.
See TIP 297.