On a multiplayer server I was playing on, my name and a couple of other names that were long (mine is 16 letters, someone else's was 13, see attached picture) obstructed the score to right of our name in the TAB player list.
How to replicate:
1. If you have a relatively long name, join any large server. Else, join a server using scoreboard commands and find a long name.
2. Hold TAB to see the list menu
Your (or any player's with a long name) score will not show up.
Possible way to fix:
Have column width adjust to the longest player's name and score length instead of a fixed width for a certain amount of columns.
NOTE: This will only work if there are at least 3 columns, so LAN worlds with only a couple of people and singleplayer worlds with scoreboard enabled will not show this bug.