When I chat using romaji, Japanese will always use si instead of shi, for example yorosiku instead of yoroshiku, siteru instead of shiteru. Do Japanese actually pronounce shi as si?
It's the difference between Hepburn romanization and Wapuro romanizaton. Adults generally use Hepburn system for person names, signboards, posters and such (し =
shi, づ =
zu, じゃ =
ja). But when they need to type ordinary Japanese sentences using romaji, they (almost unconsciously) use wapuro style because it's more efficient and unambiguous (し =
si, づ =
du, じゃ =
ja). You don't have to type
shi to get し when you can get the same character by typing
Please remember that wapuro style has nothing to do with pronunciation. That's just an input method, how they type hiragana/katakana on keyboards. Don't assume anything about pronunciation based on English alphabet.