Description fields are set to Moodle auto-format instead of showing the HTML editor (Atto in this case). This can be verified on the Moodle Sandbox in the following way as of June 14, 2018 at 11:05 am Central US:

1. Login as admin
2. Create a new course
3. Turn editing on
4. Edit settings for created Accouncements forum
5. Description field is set to Moodle auto-format

Expected behavior would be for the field to be set to HTML automatically. We are seeing this issue with both of our installations on Moodle 3.5 and with some older courses as well with descriptions being set to Moodle auto-format.