Apply suggestions from code review

Co-authored-by: Peter Bierma <zintensitydev@gmail.com>

Author: kumaraditya303

Doc/c-api/object.rst

@@ -804,15 +804,15 @@ Object Protocol
 
 .. c:function:: int PyUnstable_SetImmortal(PyObject *op)
 
-   Marks the object *op* immortal. The argument should be uniquely referenced by
+   Marks the object *op* :term:`immortal`. The argument should be uniquely referenced by
    the calling thread.
 
-   This is a one-way process: objects can only be made immortal, they cannot be
+   This is a one-way process: objects can only be made immortal; they cannot be
    made mortal once again. Immortal objects do not participate in reference counting
    and will never be garbage collected.
 
    This function is intended to be used soon after *op* is created, by the code that
-   creates it, such as in the object's tp_new slot.
+   creates it, such as in the object's :c:member:`~PyTypeObject.tp_new` slot.
    Returns 1 if the object was made immortal and returns 0 if it was not.
    This function cannot fail.