It seems to me that in the context of regexp replacements, it would be better to use 4 instead of 3 backslashes.
https://gerrit.wikimedia.org/r/c/mediawiki/extensions/Math/+/826932
However, it seems there are some 3 backslsash replacements in core
Description
Description
| Status | Subtype | Assigned | Task | ||
|---|---|---|---|---|---|
| Declined | Stegmujo | T310373 Make Mathoid Client a standalone class | |||
| Open | None | T327098 Implement Math Accessibility Features necessary for Intent attribute usage | |||
| Resolved | Physikerwelt | T302628 Implement native MathML rendering in Math | |||
| Resolved | Stegmujo | T312528 Convert Grammar related javascript to php in texvcjs | |||
| Resolved | Stegmujo | T315978 Reminder Final Checks in Implementation | |||
| Duplicate | None | T316422 PHP Coding conventions: 3 Backlsashes? |