What do you mean by that? Unicode does have double-wide characters and, I discovered recently, some other characters called 'wide' that at least are wider than one column but smaller than two in at least some monospaced fonts. Try:
* Small Hyphen-minus (U+FE63) "﹣": Seems to be >1 and <2 columns in at least some monospaced fonts.
The code unit of UTF8 is the byte, so you only deal with bytes and byte sequences. Thus no issues of byte-order and such, which you have to deal with in UTF-16 and UTF-32 (as their code units are respectively 2 and 4 bytes).