hello my name is liam. i contracted the sillygibs infection one day about 4 years ago. it started on its own like you said and no solutions i could find in google would fix it, also like you said. i tried many things. i tried playing with fresh configs, i tried reinstalling tf2, i tried reinstalling steam, i tried disabling steam cloud before reinstalling, and many other stupid things that had no effect. i even had a long back and forth exchange with valve and i tried 6 of their solutions, obviously to no avail. nothing would fix it so every day for 3 years i had to look at hamburgers and gears and springs and rubber dicks when people gibbed and it was ok at the start but eventually began to drive me totally fucking crazy. anyways one day last year after i built a new computer and installed tf2, i noticed that the sillygibs were GONE!!!
good luck bro