Badly introduced inlined references aren't detected and they don't produce a warning of any kind, which can be embarassing on large articles with lots of references, Wikipedia being a prime example.
Consider the following piece of wikitext:
This is my bold claim.ref>Some proof of my claim</ref> <references/>
Unlike a malformed named ref, which would trigger a very visible warning, nothing is reported in this case and the problem may very well go unnoticed in a very large article with tons of references. Please consider adding some check for a </ref> without a preceding <ref> to avoid this problem.
T123236 may be related to this problem.