Further explanation could be nice, e.g.

```rust
// RFC 2616 section 19.3, paragraph 3: "The line terminator for message-header
// fields is the sequence CRLF. However, we recommend that applications, when
// parsing such headers, recognize a single LF as a line terminator and ignore
// the leading CR."
```

(I'd also put it inside the branch rather than outside it, but that's a subjective opinion.)