lets say one has:
==== Q: what's up? ====
in a Wiki page. This creates an anchor like: <a name="qwhat_s_up">
When one puts a [[#Q: what's up?]] in the same page, it is indeed translated into <a href="#qwhat_s_up"> which is fine.
But if someone puts [[that-page#Q: what's up?]] in another page, then it is converted to <a href="...#q:what_s_up> which fails to take you to the corresponding section.
I find that if I apply the patch attached, that is remove the stripping of the colon in the _headerToLink function, then it seems to work fine. Now, there may have been a good reason for that stripping in the first place, so the best approach may be to make sure the [[that-page#Q: what's up?]] gets changed into <a href="...#qwhat_s_up"> instead... I'll let you know if I run in any problem with the patch I use.