Under the covers, NumeralTickFormatter just passes everthing to a JavaScript library numbro.js. Looking at their docs, I am not sure that any escaping is supported.
However, besides format strings, you can pass any actual tick formatter objects, e.g. a PrintfTickFormatter might be a better choice here:
So I think we can close this except for one note for people looking at this thread later.
Just due to the limitations of PrintfTickFormatter and NumeralTickFormatter, if you want to escape a character AND use the thousands separator, I don’t think there is a supported way to print this.
For example, if you want 2560 to become 2,560 minutes you’ll either have to go with: