This is a follow up from https://tracker.moodle.org/browse/MDL-32317

The issue is still eminent:
"If you create a wiki using the html format (others not tested) then create a new section header using h1 tags. If you also include an additional tag inside of that html tag - such as a span tag - clicking the corresponding "[edit]" link will give an 'invalid section' error."

Example:

<h1>Title0 without any styles</h1>

<h1 dir="ltr" style="text-align:left;"><span style="color:#FF0000;">Title1 (h1 style + span style)</span></h1>

<h1 dir="ltr" style="text-align:left;">Title2 (h1 style)</h1>

<h1>Title3 without any styles</h1>

<h3>Subtitle3 without any styles</h3>

It can be fixed by changing line 85 in mod/wiki/parser/markups/html.php:

$h1 = array("<\s*h{$minheaderlevel}\s*>", "<\/h{$minheaderlevel}>");

to

$h1 = array("<\s*h{$minheaderlevel}.*>", "<\/h{$minheaderlevel}>");

See also https://tracker.moodle.org/browse/MDL-70521 ("Additional HTML coding in Atto breaks Table of Content creation in Wiki") - the two issues are related!