@MSFT Brandon M:
Follow up to previous post ...
I did the following .... started a new message and took a screen shot.
Waited 3 minutes for the message to be saved (observed the "jump"), and took another screen shot.
Compared the two screen shots.
I was wrong about the bold font of the Drafts folder name causing the jump.
What I did observe is that after the message was saved, a one-line notice appeared just under the action-bar (at top of screen). This notice said: "Your message was saved in Drafts at HH:MM"
The insertion of this one line notice, and the re-rendering of the page, causes the message being composed to "jump" downward.
I waited another three minutes ... with the notice still at the top of the page .... to determine if the jump would again occur. Since the notice remained at the top of the with only the time changed, I expected the jump to not occur. But I was wrong. The jump did occur when the message was saved a second time.
What I observed, but could not capture in a screen save, was that something (one line) quickly appeared just above the text box where the message was being composed (and just below the action bar with font name, text size, Bold, Italics, Underline, etc) .... or perhaps something (one line) was inserted as the first line in the text box .... then it quickly disappeared .... causing the text of the message being composed to jump down one line, then back up one line.
You may have to dig into the HTML that is generated when the 3 minute timer expires and the message is saved .... but I suspect you will find that something is being added that causes the text of the composed message to jump down and then back up.
Hope this helps.