Wiki markup is often considered to be one of the biggest barriers to wiki adoption, yet this is something of a myth that persists from the early days of the technology. The first wikis used a markup language that used simple, one or two character tags around a section of text to make it display in a particular way. For instance, instead of using the HTML bold tag (<b>bold</b>), a wiki might surround the text with two underline characters (__bold__).
The problem was, and still is, that there was no standard for wiki markup language. The need to learn a new markup language for each wiki is seen by many as an insurmountable problem. In most cases this is little more than an excuse since most wiki markup is simple and logical and can be learned in around an hour.
As wikis matured and their use expanded beyond software developers, who are used to markup languages, wiki markup started to be replaced by more familiar word-processing interfaces where formatting is applied by keyboard short cuts or menu items and buttons on a tool bar. Now the vast majority of wikis ship with word processor functionality, and users don’t need to learn the underlying wiki markup.