A footnote typically contains a number, an arrow (↑), a space and the footnote text:
- ↑ M. Lazarus. Geisl und Sprache, 1878.
Currently, the space after the arrow is justifiable and its width varies when the footnote text uses more than one line. Therefore the first letter of the footnote text is not vertically aligned.
You can see this problem in this example (3rd footnote, Wundt) and many others in the French Wikisource. You might not notice it in other wikis which do not justify the footnotes text. Of course it may depend upon your CSS preferences.
Solution: use a non-breakable space ( or U+00A0).