Matches and Highlights disagree; only the latter shows useful results

[jmbreuer]

I've seen variants of this behavior on a number of pages, this is one fairly straightforward example.

On this page, using (?:^|\s)a[^\s$]+ (global, case-insensitive) to find/highlight all words starting with A shows 410 matches of mostly markup in the Result box:

 auto;</span></span> auto</span></span> animation:</span></span> animation-play-state:</span></span> absolute;</span></span> and</span></span> auto;</span></span> auto;</span></span> and</span></span> and</span></span> alt="Ausblenden"></a> aria-labelledby="mw-toc-heading"><input auch</span></span></span></a></li> Auflistung</span></span><span aller</span></span> alphabetischer</span></span> aufgeführt,</span></span> Anzahlen:</span></span> alt="" align="right">317</td> alt="" align="right">316</td> alt="" align="right">272</td> alt="" align="right">191</td> alt="" align="right">169</td> alt="" align="right">159</td> alt="" align="right">130</td> alt="" align="right">117</td> alt="" align="right">113</td> alt="" align="right">104</td> alt="" align="right">84</td> alt="" align="right">63</td> alt="" align="right">17</td> alt="" align="right">2</td> alt="" align="right">1</td> alt="" align="right">1</td> Abschnitts A" Abschnitts A"><span>Quelltext am am</span></span> Abschnitts Aibling">Bad<span Aibling</span></span></a> Arolsen">Bad<span Arolsen</span></span></a> am am</span></span> an an</span></span> am am</span></span> auf auf</span></span> a. a.</span></span> an an</span></span> am am</span></span> an an</span></span> am am</span></span> Abschnitts Abschnitts an Altmühl">Dietfurt<span an</span></span> Altmühl</span></span></a> an an</span></span> am am</span></span> Abschnitts an an</span></span> am am</span></span> am am</span></span> am am</span></span> am am</span></span> am am</span></span> Abschnitts am am</span></span> am am</span></span> am am</span></span> an an</span></span> Abschnitts an an</span></span> am am</span></span> an an</span></span> an an</span></span> Abschnitts am am</span></span> am am</span></span> an an</span></span> am am</span></span> am am</span></span> an Aisch">Höchstadt<span an</span></span> Aisch</span></span></a> an an</span></span> am am</span></span> an an</span></span> am am</span></span> Abschnitts Allgäu">Immenstadt Allgäu</span></span></a> am am</span></span> Allgäu">Isny Allgäu</span></span></a> Abschnitts Abschnitts an an</span></span> am am</span></span> am am</span></span> am am</span></span> Abschnitts an an</span></span> am am</span></span> an an</span></span> an an</span></span> am am</span></span> Allgäu">Leutkirch Allgäu</span></span></a> an an</span></span> Allgäu">Lindenberg Allgäu</span></span></a> am am</span></span> am am</span></span> am am</span></span> Abschnitts am am</span></span> am am</span></span> an an</span></span> am am</span></span> am am</span></span> an an</span></span> an an</span></span> Abschnitts an an</span></span> am am</span></span> am am</span></span> am am</span></span> am am</span></span> am am</span></span> an Aisch">Neustadt<span an</span></span> Aisch</span></span></a> an an</span></span> an an</span></span> an an</span></span> an an</span></span> Abschnitts am am</span></span> am am</span></span> am am</span></span> am am</span></span> am am</span></span> Abschnitts an an</span></span> am am</span></span> Abschnitts Abschnitts am am</span></span> am am</span></span> an an</span></span> an an</span></span> am am</span></span> an a.d.Laaber</span></span></a> am am</span></span> am am</span></span> Abschnitts Augustin">Sankt<span Augustin</span></span></a> am am</span></span> am am</span></span> an an</span></span> am am</span></span> an an</span></span> an an</span></span> Anhalt">Südliches<span Anhalt</span></span></a> am am</span></span> Abschnitts am am</span></span> Abschnitts Abschnitts an an</span></span> an an</span></span> an an</span></span> Abschnitts an an</span></span> Allgäu">Wangen Allgäu</span></span></a> am am</span></span> am am</span></span> an an</span></span> am am</span></span> am am</span></span> am am</span></span> an an</span></span> auf auf</span></span> Abschnitts Abschnitts am am</span></span> am am</span></span> am am</span></span> auch</span></span></span><span auch" Abschnitts auch"><span>Quelltext Agglomerationen</span></span> Abschnitts aria-hidden="true" alt="" amtlichen</span></span> alle</span></span> anklickbare</span></span> aria-hidden="true" alt="Bundesflagge alt=""</span></span> absolute;"&gt;</span></span></noscript><span aria-labelledby="p-personal-label" aus angemeldet</span></span></span></li><li accesskey="n"><span><span accesskey="y"><span><span anzumelden. aber accesskey="o"><span>Anmelden</span></a></li> aria-labelledby="p-namespaces-label" anzeigen accesskey="c"><span><span accesskey="t"><span><span aria-labelledby="p-variants-label" aria-haspopup="true" aria-labelledby="p-variants-label"> aria-labelledby="p-views-label" accesskey="v"><span>Bearbeiten</span></a></li><li accesskey="e"><span>Quelltext accesskey="h"><span>Versionsgeschichte</span></a></li> aria-labelledby="p-cactions-label" aria-haspopup="true" aria-labelledby="p-cactions-label"> action="/w/index.php" aria-label="Wikipedia autocapitalize="sentences" accesskey="f" aria-labelledby="p-navigation-label" accesskey="z"><span>Hauptseite</span></a></li><li aufrufen accesskey="x"><span>Zufälliger<span Artikel</span></span></span></a></li> aria-labelledby="p-Mitmachen-label" Artikel</span></span><span anlegen</span></span></span></a></li><li accesskey="r"><span><span aria-labelledby="p-tb-label" aller accesskey="j"><span>Links<span auf</span></span> an accesskey="k"><span>Änderungen<span an</span></span> aller accesskey="q"><span>Spezialseiten</span></a></li><li aria-haspopup="dialog"><span>Kurzlink</span></a></li><li accesskey="g"><span>Wikidata-Datenobjekt</span></a></li> aria-labelledby="p-coll-print_export-label" accesskey="p"><span>Druckversion</span></a></li> aria-labelledby="p-wikibase-otherprojects-label" anderen</span></span> aria-labelledby="p-lang-label" anderen</span></span> Afrikaans" Altenglisch" Arabisch" Aserbaidschanisch" Almanya and Alemania Armenisch" a̱ca̱cet a̱ka̱keang a̱ka̱keang Almanyayê and Albanisch" Auswahl Auswahlen anderen)">59 after-portlet-lang"><span auf Artikel anderen am</span></span> Anklicken</span></span> abgerufen</span></span> Ansicht</span></span></a></li> alt="Wikimedia alt="Powered

... and interestingly, a lot of "good" matches seem to be missing in between those results. Ie, "Bad Aibling" is shown which is in the B section of the page, while none of the towns from the A section seem to show.

Highlighting, in contrast, works as expected.

Further restricting the expression to (?:^|\s)aa[^\s$]+ (global, case-insensitive) to find/highlight only (all) words that start with 'aa' gives a Result of "No matches found", highlighting does correctly mark the first three towns under A however.