Filters with escaped parens in the complex fields can lead to JavaScript errors, making the page’s JavaScript not work.
For example, if I create a filter with any of the following strings as a line in the complex spoiler or hide fields:
frog \(*
frog *\)*
(absurd ways to craft a filter, but they function)
uploader:*\(*
uploader:*\)*
…I get one of two errors in the console:
Uncaught Error: Mismatched parentheses.
at app-c8c1030444c543edc2f1697e7e89371e.js?vsn=d:1:18018
(when an open paren)
Uncaught Error: Missing operator.
at app-c8c1030444c543edc2f1697e7e89371e.js?vsn=d:1:16743
(when a closing paren)
…and then, the whole page’s JavaScript fails to function, such as quoting a post in the forum or switching filters from the dropdown menu (visiting the Filters page directly and using the buttons to change filter is required)