Little way of spreading positive behavior
Just a thought and I'm sure this exact thing has been cover already. If someone is being salty or 'reportable' during the match and continue to get better throughout it, let them know you appreciate it and that positive attitudes help the match go better(obviously). Tell them you understand that they're having a bad day and that you are going to honor them for being friendly (whether you report them or not). It may not mean much to them but eventually it may give that player something to look forward to (a friendly reputation). Just a thought