Answer:
It depends based on the application
Step-by-step explanation:
For example, with WA, their profile picture is removed and you can only see their name. You can't see when they're last online, or if they are online at that moment. If you do decide to send a text, it will only show 1 mark instead of 2. IG will hide the message thread that you have previously had with said person for both of you. On SC, if you search for their username, it won't show up with any results.