It reveals, how fast you type, how long your breaks are, which mistakes you make and how you correct them while writing the draft, also which type of local keyboard you are using. Mouse tracking analyzes the position and speed of cursor movement unique to each person as they interact with webpages.
Combined with stylometry which works with less data (final text only), keystroke fingerprinting will completely de-anonymize you. An adversary can compare statistics about user’s typing over clearnet, then compares it to texts composed over Tor in real-time.
I use the method kwrite–>browser in tor, if I have to use a VPS, would a virtual keyboard be useless to avoid keyword fingerprint between clearnet, where I use that of my pc, and VPS?
I am talking just about keyword fingerprint