Replicated across all browsers & devices I’ve tried. Rich text and formatted notes are fine, as is the Best Alternative view of Markdown documents in both the solo and side-by-side views, but the plain-text view, and plain-text documents, no longer wrap as they did in DT3 Server.
(On the upside, I’d never have noticed this without all the improvements to Server in DT4 that have got me using it for a much wider range of tasks; I rarely used to edit Markdown documents in Server and now I think I’m going to be doing it all the time.)