I feel that formatting should be used for emphasis sparingly. Excessive use of contrast formatting has a negative effect on readability. The primary use of formatting is not for emphasis but to aid readability of code and distinguish text types. Version numbers do not need to be emphasised with formatting and are most comfortably read as a normal part of the text.
Keyboard formatting is useful for showing key combinations like Ctrl+Alt+T. Some people, including me, also sometimes use it for buttons that appear in GUI dialogs, like the button at the top right of the main page area here that says Ask Question. This decision seems reasonable to me, because the effect of
<kbd> formatting is to make the text look like a button, hopefully aiding recognition. Please note that by "button" I do not mean everything that is clickable - to distinguish GUI menu items that are not buttony in appearance I use bold or italic formatting which is less obtrusive than