That second bullet point seems to be the case when there are changes made to the Markdown parser that cause exactly the same Markdown to produce a slightly different HTML rendering (remember, the Markdown is parsed only at the time of posting, and the rendered HTML is saved after that). The system sees this difference and thinks that you changed something in the body, and it rejects it.

15 minutes later, the question is actually showing up as featured.

possible duplicate of Manufacturer & Company tags are back. Again

I think that this should be featured for some time. Additionally, I've suggested edits to the tag wiki for the new tag tag-cleanup-weekends.