I am not saying that your implementation of count+ is wrong.  It meets
the specs of srfi-1.  But so did the previous implementation.  And so
does mine.

And since there is otherwise no actual length operator of any kind
working for dotted lists, I want one.  The previous implementation was
actually trivially the same as

(define (length* lst)
  (catch 'wrong-type-arg
    (lambda () (length lst))
    (lambda _ #f)))

and consequently was trivial to write using existing length functions in
the C API.

And I need my variant of length+ to fix things like take-right which
currently bomb out on large lists with a VM error and are _required_ to
deal with _both_ proper and dotted lists.

Which is awkward to do without a length operator working on both proper
and dotted lists.

-- 
David Kastrup