It has been just a month since Pokémon Go players began noticing that Niantic had started "shadowbanning" accounts that use third-party trackers and bot software, limiting them so they only see common Pokémon. Now, the company is going further to ensure ill-gotten beasts are publicly identified as such and don't negatively impact the multiplayer experience.
With the announcement of Raid Battles and the new battle features, we are staying true on our commitment to ensuring that Pokémon Go continues to be a fun and fair experience for all Trainers. Starting today, Pokémon caught using third-party services that circumvent normal gameplay will appear marked with a slash in the inventory and may not behave as expected. We are humbled by the excitement for all the new features we announced yesterday. This is one small part of our continued commitment to maintaining the integrity of our community and delivering an amazing Pokémon Go experience.
What Niantic means by Pokémon "not behav[ing] as expected" is unclear, but the wording suggests these beasts may not be effective in the game's recently announced raid battle and expanded gym features. That coming overhaul will allow six unique Pokémon to be assigned to each individual gym, and it will let players team up for cooperative raids against ultra-powerful Pokémon. We're guessing Pokémon marked with a slash won't be able to fight for those coveted gym slots, at the very least.