Change to disable replies to replies

There are very few reasons you'd ever want to do this and I think it's
more helpful to just disable it altogether. A reply should be thought of
as **creating a new thread**, and if you have a response to the thread
that's created then it should be posted as a **comment**.

Making a new thread as a response to an existing thread is an advanced
action and I think the simplicity is worth the small reduction in the
degrees of freedom for advanced users. Maybe I'll change my mind?

src/pages/views/components/post.js

@@ -44,6 +44,8 @@ module.exports = ({ msg }) => {
     'value.meta.thread.target',
     false
   ))
+
+  // TODO: I think this is actually true for both replies and comments.
   const isReply = Boolean(lodash.get(
     msg,
     'value.meta.thread.reply',
@@ -76,9 +78,12 @@ module.exports = ({ msg }) => {
   }
 
   if (isReply) {
+    // True for comments too, I think
     messageClasses.push('reply')
   }
 
+  const isFork = msg.value.meta.postType === 'reply'
+
   const postOptions = {
     post: null,
     comment: [
@@ -150,7 +155,7 @@ module.exports = ({ msg }) => {
           class: likeButton.class
         },
         `❤ ${likeCount}`)),
-      (isPrivate || isRoot) ? null : a({ href: url.reply }, 'reply'),
+      (isPrivate || isRoot || isFork) ? null : a({ href: url.reply }, 'reply'),
       isPrivate ? null : a({ href: url.comment }, 'comment'),
       a({ href: url.json }, 'json')
     ))