When i register og login on the wiki the First CAPTCHA character starts on the line before input box and then rest of the CAPTCHA is to the left of the box. So maybe better to make a new line before the CAPTCHA text and maybe use or something to make sure the text dont wrap.
Fixed/circumvented : There is no visible captcha anymore, this task is done through JavaScript automatically, then the whole CAPTCHA test is hidden from the user. See https://www.dokuwiki.org/plugin:captcha If js is disabled on user browser, the old visible captcha is displayed (and in this case there is the old display bug)