When using the atto editor and either editing, or copy and pasting into the editor, it starts to render random style tags, and other things that look very odd. None of this shows up in the editing mode, only when viewed. Also, clicking "preview" seems to render something differently than when clicking save without previewing. (see screenshots in order)

I've developed a VERY simple test on qa.moodle.net to reproduce and show ONE EXAMPLE of this problem:

1) Create a blank HTML wiki
2) Once the empty wiki is created, click "Edit"
3) type the following DO NOT COPY (just to prove that it's not an issue of copying metadata from the source): https://test.com
4) highlight the text, and create a hyperlink using https://test.com as the source. it does not matter whether you check or leave unchecked the "open in new window" checkbox
5) Place the cursor at the end of the line, and press enter
6) click the bullet list button, and type "test"
7) Press "Enter", then click the "Show more buttons" button, then click the indent button and type "test"
8), press save
9) you should see the following output shown in image qamoodle.png