Function escape 

pub fn escape(input: &str) -> String

Escape a string for safe inline rendering inside Markdown.

The goal is injection safety, not escaping every punctuation mark. We:

• entity-encode HTML specials (<, >, &) so raw HTML can never be injected into a rendered comment;
• backslash-escape the Markdown characters that let attacker text break out of inline context — code spans (`), emphasis (*, _), links/images ([, ]), tables (|), and a literal backslash;
• flatten control characters (including CR/LF) that could forge new lines or block-level constructs.

Cosmetic-only characters (. - ! + # ( ) { }) are left as-is: with newlines stripped they cannot start a block, so escaping them only produces noise.