Just tried to fix note display in post #1464963 to put black text on white background, and the <span> tag isn't working. The display essentially ignores the entire tag.
I thought I might be mistyping something, even though it all looked right, so I went to check some of my previous notes using <span> and <div>. The couple of examples I looked at had lost all effects from those tags, and clicking to edit showed that all formatting within the tags is now gone. (E.g., if a tag originally had "<span style ="font-size:400%; color:white; background-color:black>", it now just reads "<span>".
Now, I'd seen similar lack of tag content display when we were originally making the transition to 2.0, but at least that was a cause I was aware of. Before I panic or get upset, how much concern should this actually be worth?