plugin_pagetree_children_span is hijacking the contents of a paragraph

I noticed on https://confluence.atlassian.com/display/DOC/Migrating+to+Another+Database that the paragraph in the third dot point of the page was mangled:

If you copy paste the text (or go into the editor), you get the correct paragraph:

Similarly, if the dataset is not large, you can use this method to upgrade your database to a new version of the same database. Note: You do not need to migrate your data if you are upgrading the database in place.

I had a look at the page source and found the following: