@indojin Very funny "privacy" :-) You are sending your messages to the Internet as the same User, where your posts can be tracked and analyzed (if somebody would care...) but you obfuscate your Username inside your own device for yourself and for applications, which _you_ installed and for which you personally gave permission to read accounts... Actually, if some application can read your account name, it can read data, which is stored with this account...
Since Android 6.0 accounts protection was tightened: application doesn't need such a dangerous permission to read its own accounts...
Conclusion: this feature of Twidere doesn't look like substantial privacy enhancement. In order to protect your privacy inside your device I would recommend to use device-wide protection measures (including Android upgrades and careful selection of applications) instead of such kludges inside individual applications.