The mods don't IP ban you. What happens is you get your account permabanned from a big subreddit like r/politics. Later in another account, you use r/politics again, either because you think the ban was clearly bullshit or you just forgot about the ban on an old account. Then reddit's site tools kick in, see your connected accounts, and IP ban you for "ban evasion." Individual mods won't IP ban you, but the site will IP ban you for daring to evade the bullshit decisions of clearly biased tinpot dictator subreddit mods.