Change character used to conceal ::

[MrDetonia]

It seems that currently, the characters :: are concealed by ⦂ (U+2982).

This seems to cause issues on some systems - it was not visible on mine, and several other people I asked to test.

Would it be better if ∷ (U+2237) was used instead? This character seems to be visible on all systems tested, and makes more sense to replace :: (to me at least).