When concatenating styles, output depends on the order of the styles. This is intentional, but in some cases it's counterintuitive for the user. For example:
alternate|double test → 𝕥𝔼𝕤𝕋, but
double|alternate test → 𝕥𝕖𝕤𝕥
It might be a good idea to introduce an mechanism ordering the styles automatically.