I see others typing different characters. I cannot figure out how to do it in runescape chat, for example upside-down question mark ÃÆââ¬Å¡Ãâÿ

some keyboards are designed with this for their language, others i belive is using SHIFT and then different symbols like ! above 1. there should be some sites explaining how it works and what buttons to use.

You need to use a foreign keyboard setting to use those characters w/o using ALT.