Microsoft and 343 Industries announced more bans in Halo: The Master Chief Collection through a blog post. One particular reason for players getting banned caught the eye since it should finally get rid of farmers who don't actually participate in a match.
Some players like multiplayer games for the thrills they offer and some just want to rank up. Both groups really want to rank up but the latter is hell-bent on doing so even if it means they will forego the actual gameplay experience. Unfortunately, since there is no way to separate them into different lobbies, they tend to ruin matches for those who just want to enjoy the game.
This happens through the so-called AFK farming when a player just enters a match and goes on about some other business while standing in the same spot or just dying repeatedly either at the expense of their team or everyone in a deathmatch.
Therefore, it is no surprise that the developers are banning for such behaviour and 343 already did it before. However, they announced another ban wave will be going out soon while emphasising the three main behavioural culprits behind it.
AFK and macros had the first mention. The latter is bannable pretty much everywhere while the reasons for AFK bans were explained in the paragraphs above.
Sword Lining is a term that might confuse some people. In Halo's Grifball mode, players tend to line up and farm kills on each other. Meanwhile, those who are in it for the fun of playing the game are either insulted or just stuck watching two lines of farmers killing each other.
Firefight suicides after reaching maximum XP is the third reason 343 listed. Intentionally dying is considered unsportsmanlike conduct in all competitive games and Halo MCC titles are not an exception.