Updated September 7, 2018
The Markdown Pro app collects no personal or anonymized data from your usage of the app regardless of whether the Premium upgrade was purchased. Period. This is due to the fact that there are no third-party advertisements nor any analytics whatsoever in the app. There are first-party advertisements in the form of popups that remind you to upgrade to the Premium version of Markdown Pro, but they don't collect any of your data either.
If you email me to request support, suggest a feature, or for any other reason, I will keep the email for one month. I use secure ProtonMail and Tutanota email accounts to protect your data, and I encourage you to email me from one of these services to protect your own privacy. After one month I will securely store your email for a maximum of one year with all personal information removed (including email addresses and signatures) so that I may improve my customer service and the Markdown Pro app. When contacting me, you may request that I delete all of our correspondence, at which point I will comply as soon as I can.
mshmoustafa.com does not collect any data by means of cookies, cache, or session data of your usage of the website.