Comment by thematrixadmin

What about writing data in markdown format, physically on the HDD. You can use bunch of different both online and local tools which will probably stay supported in the future. There is also no problem with implementing your own markdown editor (nice side, pet project as well). I store and run small server on my RPi, accessible through my phone and desktop. If I'd like to show the text to somebody I can easily copy it as a plain text, Word format or export it to HTML or PDF.