I’m dissatisfied with what appears to be the standard character being used after a footnote, to denote a link back to the referencing text. The character I’ve been seeing is ↩ (0x21A9), but it’s too similar to the standard “undo” symbol, and it doesn’t point up, which should be the natural direction to point, when pointing from a footnote to its referencing text.
Here are the up-pointing arrows that I see in unicode. I’m sure there are more:
↩ 0x21A9 (not this one)
↟ 0x219F
↥ 0x21A5
⇧ 0x21E7
⇫ 0x21EB
⇮ 0x21EE
⌃ 0x2303
⍐ 0x2350
⤊ 0x290A
⤒ 0x2912
⤴ 0x2934
⤻ 0x293B
⤾ 0x293E
⬆ 0x2B06
￪ 0xFFEA
My favorite for this purpose, at least at first impression: ⤴ (0x2934).
0x290A, 0x2912, 0x293B, 0x293E all fail to render on my phone, which has stock android 5 fonts. Before choosing one of these characters, I should find out how well each of them are represented in fonts across various devices.
At second look, from my phone this time, ⇧ (0x21E7) is my favorite. Very easy to see, and very understandable for this purpose. I like that, unlike ⤴, ⇧ has no left-right component or implication. Instead, ⇧ is obvious, without being imposing, and inarguably points to something above.
See also: Unicode Lookup: convert special characters.