Maybe I need to stop dropping off the Internet. Sorry about rlgallery.org downtime. Sometimes the hosting company reboots the server, and then I have to find out about it and manually restart the Web player. But if the scoreboard page is up, you should be able to play via SSH.
About the 10% death tax: the original developers wanted to give people a tough choice between quitting with a higher score and maybe surviving to do even better. But nobody ever quits.
About items disappearing and reappearing: yes, certain monsters will pick them up.
About the mechanics: they are really quite simple, unlike later games which apply complicated formulas to everything.
What affects how much damage you take when you get hit?
The monster. Each monster type has a particular number of hit dice with a particular number of sides. They all get rolled and added up.
What affects your ability to dodge an attack?
The monster's level and your AC.
What affects how much damage you do when your attack hits?
Your weapon. It has hit dice just like monsters do.
What affects whether you hit your opponent?
Your experience level and the monster's AC, just like when it attacks you.
Dexterity does not exist in Rogue. Leveling up gives a 5% boost to your chance to hit, every time.
Maybe you don't understand everything, but you and Pertinax are certainly tearing up my high score list.