Why does TOML code block formatting look so bad?

I have a Stack Overflow answer here that includes a TOML code block.

I have tagged the code fence:

```toml

But the resulting highlighting looks very poor and does not even highlight the comments correctly.

Given TOML's prevalence in the Python and Rust communities, this surprised me. Is the highlighter for toml broken or missing? Am I annotating the code block incorrectly?