Remove character from permalink

to achieve that is not easy, this to say almost impossible, the permalinks are made by the slugs, and the slugs have a function called sanitize_tittle(), this is probably what is doing that to your permalink.

A slug consists of solely lowercase alphanumeric characters, dashes
and underscores, without 2 or more dashes in a row (sequences of
underscores are allowed). Furthermore, a slug cannot start or end with
a hyphen.

This to say that for all I know isnt possible, only changing the wordpress functions that make the slugs, but doing that can probably bring you some issues at long term on your permalinks, also can disapear on a wordpress update. anyhow is that.