[P3981] More updates

Author: brevzin

3981_optional_ref_inplace_vector/optional-ref-inplace-vector.md

@@ -124,6 +124,8 @@ if (not sr.empty()) {
 
 This follows the general principle that ranges are simply more convenient for users than iterators, because you only need the one object rather than two.
 
+This API is quite unlike a few algorithms which return an iterator, like `std::find`, where the iterator itself is specifically desired. In this case, the return isn't really conceptually a single iterator — it is very much the range _starting from_ that iterator. Hence, `subrange` is the more appropriate return type.
+
 # Why not do this?
 
 [@P3830R0]{.title} argues that we simply should not make this change, mostly on the basis that it is new. Which, yes, the specific specialization `std::optional<T&>` is new, and it took unnecessarily long to adopt it after `std::optional<T>` was adopted (despite its existence in Boost for decades, and proliferation across many other `optional` implementations). But the notion of an optional reference in general is not new, and we have a lot of experience with it outside of the standard library — and even outside of C++. The Rust standard library returns optional references from many APIs quite liberally.

3981_optional_ref_inplace_vector/p3981r0.html

@@ -843,6 +843,14 @@ <h1 data-number="3" style="border-bottom:1px solid #cccccc" id="iterator-or-subr
 <p>This follows the general principle that ranges are simply more
 convenient for users than iterators, because you only need the one
 object rather than two.</p>
+<p>This API is quite unlike a few algorithms which return an iterator,
+like
+<code class="sourceCode cpp">std<span class="op">::</span>find</code>,
+where the iterator itself is specifically desired. In this case, the
+return isn’t really conceptually a single iterator — it is very much the
+range <em>starting from</em> that iterator. Hence,
+<code class="sourceCode cpp">subrange</code> is the more appropriate
+return type.</p>
 <h1 data-number="4" style="border-bottom:1px solid #cccccc" id="why-not-do-this"><span class="header-section-number">4</span> Why
 not do this?<a href="#why-not-do-this" class="self-link"></a></h1>
 <p><span class="title"><span class="citation" data-cites="P3830R0"><a href="https://wg21.link/p3830r0" role="doc-biblioref">[P3830R0]