Have you made any custom level up messages in the morrowind.ini file? If so, what have you made it say and for what level?
For the same reason as Master1076, I didn't want to write them myself. But luckily, long long ago, I found a random post on a forgotten forum where a player had written leveling messages for up to level 99 with a few "Congratulations!" fillers here and there. No more default message at each level up once you reach the last vanilla message. It's pretty neat.
If you guys are interested I can copy them over in a spoiler.