I'm aware of the discussions. I also gave up trying to get NULL into TOML and I think I'm reference in one of those issues. Personally I do not create TOML configs where absence of key has a meaning, but I'm also exposed to other people's TOMLs where this is an actual issue with all the consequences this causes.
And that ignores the issue of nulls in arrays which are sometimes needed. For instance I have been exposed to parameterized SQL queries in TOML where you need to use the empty object to represent NULL, a particularly absurd incarnation of this.
I'm not saying there aren't reasonable and valid use cases, there obviously are. But there are also downsides, so the question is how it all balances out. Almost every feature that has ever been added to anything has reasonable and valid use cases, but clearly not everything should have all the features.
And that ignores the issue of nulls in arrays which are sometimes needed. For instance I have been exposed to parameterized SQL queries in TOML where you need to use the empty object to represent NULL, a particularly absurd incarnation of this.