Switching between editors changes markup with + characters

I got an error when I was switching between the wiki markup to rich text editors.
I think it was related to the use of "+" with the underline and italic formatting.

In general, the following markup entered on the markup page:

_+aaa+_\+_+bbb+_\+_+ccc+_

is shown correctly on the rich text page (underlined italic letters), but a switch back to the markup page mutilates the markup to:

_+aaa+_+_+bbb+_+_+ccc+_

which then shows incorrectly on the rich text page as all underlined italic (including "+").
Yet another switch back to the markup page shows the following:

_+aaa+__+\+bbb+__+\+ccc+_