NFC: Accumulated nits in comments

Mostly, promote some inline commentary to doc comments.  A typo and some stale
text can go, too.

src/mem/freelist.h

@@ -271,12 +271,6 @@ namespace snmalloc
    *
    * Adds signing of pointers in the SNMALLOC_CHECK_CLIENT mode
    *
-   * We use the template parameter, so that an enclosing
-   * class can make use of the remaining bytes, which may not
-   * be aligned.  On 64bit ptr architectures, this structure
-   * is a multiple of 8 bytes in the checked and random more.
-   * But on 128bit ptr architectures this may be a benefit.
-   *
    * If RANDOM is enabled, the builder uses two queues, and
    * "randomly" decides to add to one of the two queues.  This
    * means that we will maintain a randomisation of the order
@@ -348,7 +342,7 @@ namespace snmalloc
      * Adds an element to the builder, if we are guaranteed that
      * RANDOM is false.  This is useful in certain construction
      * cases that do not need to introduce randomness, such as
-     * during the initialation construction of a free list, which
+     * during the initialisation construction of a free list, which
      * uses its own algorithm, or during building remote deallocation
      * lists, which will be randomised at the other end.
      */

src/mem/localcache.h

@@ -68,6 +68,9 @@ namespace snmalloc
     : remote_allocator(remote_allocator)
     {}
 
+    /**
+     * Return all the free lists to the allocator.  Used during thread teardown.
+     */
     template<
       size_t allocator_size,
       typename SharedStateHandle,
@@ -77,8 +80,6 @@ namespace snmalloc
     {
       auto& key = entropy.get_free_list_key();
 
-      // Return all the free lists to the allocator.
-      // Used during thread teardown
       for (size_t i = 0; i < NUM_SIZECLASSES; i++)
       {
         // TODO could optimise this, to return the whole list in one append

src/mem/remoteallocator.h

@@ -71,13 +71,15 @@ namespace snmalloc
       return bk == front;
     }
 
+    /**
+     * Pushes a list of messages to the queue. Each message from first to
+     * last should be linked together through their next pointers.
+     */
     void enqueue(
       CapPtr<FreeObject, CBAlloc> first,
       CapPtr<FreeObject, CBAlloc> last,
       const FreeListKey& key)
     {
-      // Pushes a list of messages to the queue. Each message from first to
-      // last should be linked together through their next pointers.
       invariant();
       last->atomic_store_null(key);
 
@@ -93,9 +95,11 @@ namespace snmalloc
       return front;
     }
 
+    /**
+     * Returns the front message, or null if not possible to return a message.
+     */
     std::pair<CapPtr<FreeObject, CBAlloc>, bool> dequeue(const FreeListKey& key)
     {
-      // Returns the front message, or null if not possible to return a message.
       invariant();
       CapPtr<FreeObject, CBAlloc> first = front;
       CapPtr<FreeObject, CBAlloc> next = first->atomic_read_next(key);