Due to his conduct, I consider Matt a bad actor, at this point. Combine that with other perhaps dubious allegations in other lawsuits[1] against Matt.
If I were using SimpleNote, I'd question the privacy of my notes. The notes aren't encrypted[2]. I'd have concerns if my notes have been/will be grepped through for "juicy" content, or if I were to publicly criticize the owner, embarrassing details be made public in some fashion.
Same for Day One. I'd stop using it immediately and cut my losses. Obligatory link[3].
I don't use any of Automattic's products except WordPress, but previously, if I were going to use a cloud-based notes app, I'd have probably used SimpleNote, based on my previous impression of Matt as this stoic do-gooder.
This is a good lesson in that you don't really know the real person behind these public personas. Do not make critical decisions based on these personas.
1. https://github.com/bullenweg/bullenweg.github.io (I have zero affiliation with this site)
2. https://simplenote.com/help/#encryption
3. https://dayoneapp.com/guides/day-one-sync/end-to-end-encrypt...