Recently, I "Markdownified" the online version of the NEWS file and added some categories to avoid repetitive sayings like "... to be ML compatible.... will be removed from Octave 7...." which is boring to read:
Now I am able to read the changes on my smartphone without horizontal scrolling as well ;-)
Are there any objections against using Markdown for the NEWS file in general? Octave already uses Markdown for the README file and the current style of the NEWS file is quite close to Markdown anyways. This makes it easier to create a good looking news announcements without to much post-processing on the website.
By using a plain text editor the file is still readable  (even better if the editor supports Markdown-syntax highlighting). The only drawback as with README is, that we cannot help the editor by adding a prefix like "NEWS.md". This would violate the GNU Standard in automake .
If there are no objections, I would merge my NEWS-5.1.md
changes with the stable branch (omitting some website related additions) and Markdownify the current default branch.