Steps to reproduce the issue

Create an article. Insert
<hr id="system-readmore" style="width: 1013.75px; word-spacing: 0px;">
instead of
<hr id="system-readmore"/>
into an article to create an introtext.

Expected result

ignores additional parameter and splits text into intro+fulltext

Actual result

doesnt split, ignores hr.

Additional comments

Dont ask me why or how they added the parameters, they did.

possible solution

change regex-pattern in libraries/legacy/table/content.php:128 (function bind)
from

$pattern = '#<hr\s+id=("|\')system-readmore("|\')\s*\/*>#i';

to

$pattern = '#<hr\s+id=("|\')system-readmore("|\')[^>]*\/*>#i';