Forum post word count not reflecting the size of some posts as they are displayed to users

NOTE: You need to be able to access database table content to test this issue.

Testing that when posts, edits and replies are posted, script content is stripped before being written to the database, and content loads correctly. Also testing word count works as expected.

Pre-requisites and setup

1. You need to be able to access database table content to test this issue.
2. You need a Moodle site with a course with a forum activity created.
3. Log in as admin, and open the forum.
4. Click the cog (actions menu) on the right, and select 'Edit settings'.
5. Expand 'Attachments and word count', and set 'Display word count' to 'Yes'.
6. Click 'Save and Display'.

Testing
You should still be logged in as admin, and on the forum summary page (from the last step of setup).

1. Click 'Add a new discussion topic'.
2. Add a discussion topic as follows:
   Subject: "What do".
   In message, click 'show more buttons' (the top left icon in Atto), then click the HTML button (bottom right icon in Atto). Paste in the following text:

   <p onclick="alert('boop');">Snoot is booped</p>

   <script>alert('Boop the snoot');</script>

   <img alt="Boop the Snoot." src="https://proxy.duckduckgo.com/iu/?u=http%3A%2F%2Fwww.geekfill.com%2Fwp-content%2Fuploads%2F2015%2F08%2FBoop-the-Snoot.jpg&f=1">

3. Click 'Post to forum'.
4. Open the database for your Moodle site, and access the mdl_forum_posts table.
5. Find the most recent post (the one you just created), CONFIRM only the onclick event on the paragraph, and the <script> content have been removed, so the message field is as follows:

   <p>Snoot is booped</p>

   <img alt="Boop the Snoot." src="https://proxy.duckduckgo.com/iu/?u=http%3A%2F%2Fwww.geekfill.com%2Fwp-content%2Fuploads%2F2015%2F08%2FBoop-the-Snoot.jpg&amp;f=1" />

6. Return to the forum and open the 'What do' post.
7. CONFIRM the post is visible, with 'Snoot is booped' and the image both appearing.
8. CONFIRM The word count below the image says '3 words'.
9. Click 'Edit', open the HTML editor, and overwrite the whole post with the original content from step 2 above, then save.
10. CONFIRM the post still appears correct and CONFIRM the word count still says '3 words'.
11. Go back to the database and refresh your view of mdl_forum_posts.
12. CONFIRM the content of 'message' in the post still matches the example in step 5.
13. Return to the forum post in Moodle.
14. Click 'Reply'.
15. Open the HTML editor and paste in the content from step 2, and click 'Post to forum'.
16. Go back to the database and refresh your view of mdl_forum_posts.
17. In the row for the new reply post, CONFIRM the message content matches the example in step 5.
18. Return to the forum post in Moodle.
19. CONFIRM the content in the reply appears correctly and CONFIRM the word count still says '3 words'.