• Attempt to connect to community server that requires mods
• All missing mods are automatically put into download queue
• All mods necessary for server are activated
• Leave server
• All mods downloaded for server stay active
• Launch into editor/tutorial/self hosted combat ops
• Unknowingly and unintentionally play with mods loaded

OR

• Attempt to connect to community server that requires mods
• All missing mods are automatically put into download queue
• Cancel connecting to server
• All mods automatically added to download queue continue to download and are automatically set active as they finish
• Launch into editor/tutorial/self hosted combat ops
• Unknowingly and unintentionally play with mods loaded

Whether manually downloaded mods are automatically enabled or also disabled to keep in line with the automatic server mods could go either way. Also, I don't remember seeing any sort of mod warning when I played the tutorial modded with ACE, which you would normally very clearly see in Arma 3 if you'd launched the game modded without thinking (and whenever on a loading screen), so I was unaware the mods had broken the tutorial, and I blamed the game. I'm sure I'm not the only one confused about that, especially as many people would first try joining a random server (and you'd see modded community servers at the top of the charts) and then the tutorial afterwards (I'd only tried it for a second time afterwards because I'd realized there was an achievement for doing all sections in one go that I'd missed). While I'm now aware there is one on the load screen, I don't think it's nearly clear enough to grab the attention of someone not looking for it (and you wouldn't be looking to check if you game is modded if you never activated any mods.