currently format can detect if you compile with /utf-8 and activate a fast path in the string parser (we can search for control characters using a simple byte search, instead of decoding all the code-points). In reality we can do this search for almost any encoding, with the exception of non-self-synchronizing multi-byte encodings.

In micro benchmarks the fast path can be 10-15x faster than the slow path, so getting the fast path for 1252 would have major performance benefits for users.