Wikipedia:Unicode
Wikipedia uses Unicode (specifically UTF-8) to encode text in articles and article titles. Unicode is a successor of encodings like latin-1, which only handles european languages (and some others). With Unicode, Wikipedia has support for a large part of the world's scripts.
Browser support
Most modern browsers support Unicode, and most users will not find any problem editing Wikipedia.
For older browsers, MediaWiki, the Wikipedia software, serves the wikitext in a safe mode upon editing. Characters that cannot be represented in ASCII are temporarily converted to hexadecimal character references, looking like ሴ. Existing hexadecimal character references get an additional leading zero so they are not converted to actual characters when the page is saved, and look like ሴ. Likewise, to create a hexadecimal character reference in safe mode, not the character itself, a leading zero should be added. One can check whether safe mode is used by editing this section. If M looks like M rather than M, safe mode is used.