Strangely, no one seems to have mentioned this bug here earlier although it has not been newly introduced with the latest beta:
When you type a note in the editing pane of DT3’s main window there is no word wrap. While typing longer lines the characters vanish behind the Inspectors pane (if visible) or in the limbo between the edge of the window and the desktop.
This applies to Markdown, RTF, and plain text notes. Formatted notes, though, have word wrap.
I tested in in Widescreen mode.
After toggling the Inspectors pane or selecting a different item and then return to the note its word wrap is active.
Formatted Notes have a margin, as they’re just HTML.
RTF files indeed wrap, according to the margins set on the ruler.
Markdown and plain text in editing mode have no concept of a page, so there is no explicit margin to wrap to. Markdown would have a margin when rendered, again, it’s just HTML content.
@cgrunenberg would have to assess this situation.
I couldn’t reproduce this over here. Did you zoom your docs?
At least in case of plain/rich text zoomed documents should be still wrapped. Which macOS version do you use?
MacOS 10.14.6 Beta (18G29g).
And indeed—if there is no zoom the wrapping while typing works as it should.
Hard to tell whether this is a glitch of the 10.14.6 beta but at least over here plain/rich text and Markdown documents are even wrapped after using zooming. Anyone else experiencing this?
After playing around with zoom I can get a little more precise: There actually is word wrapping but it does not fit the pane width when the zoom is set to more than 100%. My guess is that the wrapping kicks in at the line length when the text at 100% zoom would have hit the margin (minus padding of course).
A correction regarding RTF notes: They do properly wrap but only when the ruler is visible.
All of this is not font related. I tested it with a customized font and with standard ones.
I made a little screencast:
The Weird Wrapping.mov.zip (10.0 MB)
Thanks for the screencast! And no worries about typos! I can spell fantastically but my typing wouldn’t show that fact! 
The issue appears to be the zoom level on the document is being applied every time you are creating a new document. It doesn’t reset the zoom level when you create a new document.
- If you pressed Command-0 and typed, it should wrap as expected.
- Then create a new document and that should wrap as expected.
- Then zoom up in that document and create a new one, it should type past the page edge.
