I also prefer to write my stuff offline and than paste it to a web interface. That works great, until you write markdown and paste in into Confluence. Instead of just accepting markdown and formatting it in the same way it does when you type markdown, Confluence puts it between code tags..

Jira does this better, but is still weird with their text formatting. There are two different kinds of input fields, one of them accepts markdown, the other one some other kind of markup language. Copying some formatted text from one of the inputs to the other doesn't work because of this.