Clawstripe said:
Personally, I liked ♥ because it told me exactly what was tagged at a glance, was part of the standard ASCII set (ALT+3), and matched the other card suits – ♦, ♣, and ♠. (There are also other symbols used as tags – ♂, ♀, and ⚥, to only be used when the symbols themselves appear in the picture.) Then someone changed it to <3. True, it's a common smilie, but it breaks the pattern and doesn't match the other symbols.

Actually I'm wondering, why were the symbols kept as opposed to their word counterparts (e.g. male_symbol --> ♂)? It seems to just be more difficult to tag, especially on mobile devices. Some symbols were more favored as tags while others got aliased to word combinations (like ☭ --> hammer_and_sickle).