While Flow changed anonymous IP handling, blank IP addresses led to topic participants appearing in a white typewriter text block. This happened because wikitext parsing of a message starting with a blank results in pre-formatted text. In eval.php,
echo wfMessage( 'flow-topic-participants', 2, 2, '', 'second person' )->parse();
(note the empty string for first participant); this prints
<pre>and second person
We fixed that bug, but it's wasted effort doing this level of wikitext parsing if we don't need to, and it's prone to embarrassing HTML output. Niklas on mediawiki-i18n list commented
Is there any other wikitext besides the magic words? You could just use ->text() instead of ->parse().
and sure enough if you call text() instead you avoid the additional parsing. I didn't test this message's complex GENDER handling in a language where it matters, but we should check all our messages using parse() (about 13 of them in PHP) and see if we can switch them to ->text(), or escaped() if they're directly output, or even plain(). See https://www.mediawiki.org/wiki/Manual:Messages_API . Use of parse() where we don't intend to be converting wikitext constructs into HTML seems about 25% slower on this string in my dopey testing, and could cause some display bugs.