Posted a PR, I'd appreciate if someone with a fresh pair of eyes would take a look:
https://github.com/phpbb/phpbb/pull/4631
Some test fixtures I created in previous PRs may be incorrect in that their entities may not be encoded. Most of the time I manually copy/paste data from phpMyAdmin into the XML file and I may have forgotten to use CDATA field in some places, meaning that some tests may be run on incorrect data. If that's the case, the kind of bugs it would produce is that something would stop working when it contains HTML special chars like the two topics above.
On second thought, those test fixtures simulate the return values of the data_access\get_* functions, so their content should not be encoded.