[[Free Links]]. Alternately, you could just turn off the SubPage feature if you don't use it.
I experimented with the "word break" requirement mentioned above, but found that it breaks a common subpage feature very badly (subpage links like /InvalidLinkGenerated no longer work). I still don't consider this to be a bug--the wiki parser rules occasionally have unintended consequences. There are several workarounds for this problem (the simplest being to use nowiki tags around unwanted links), so it will not change in 1.0. --CliffordAdams