Hello Zorkas,
I dont know the answer but I'll try to steer you in the right direction. I never heard of that happening before.
For the administrator
Heres a link to pm one of the staff (I just picked a staff at random as I have no idea which staff member to ask) If and only if I had to take a guess, I would say its maybe for maintence.(I can't think of any other reason then that) Maybe messages got filled up so it deleted the oldest one. Maybe it gets removed after so many years. I have one thats in 2016.
https://forums.comodo.com/index.php?action=profile;u=892247
If your going to look into it, I hope you get a answer
