I don't have any context provided to base an overview on. You've indicated the category exists on Wikimedia but haven't included the actual description, contents, or documentation that would let me accurately explain what "Character-substitution templates" are and why they matter. Could you provide the specific information from that category page?
AI-generated from the Wikipedia summary — may contain errors.
Templates enabling the use or insertion of a character or characters that otherwise: are or can be "escape" or reserved characters within Wikipedia (due to HTML, wiki markup, etc; e.g. {{!!}} for two consecutive vertical bar ("pipe") symbols (" ||");
may compromise HTML, wiki markup, etc that precedes or follows them (e.g. single quote marks beside wiki markup for italics or bold text).
via Wikidata sitelinks · CC0
Discovered by embedding cosine similarity (sentence-transformers MiniLM, 384-dim).