tbh, I missed that, sorry.
reading it now, I feel it falls short of being too helpful though, as it only scratches the surface. because of that, I believe you would better reference the post I link below, without explaining too much. It will only raise more answers.questions like this
this is what I meant Updating Templates with the new default values in 2021.10.x
well I do not agree with you there, and stressing that idea probably doesnt help… I honestly dont see what is difficult in seeing what a filter (or the function variant) does.
just state that for some operations the entities need to be of the correct type, and the type-casting filter/function takes care of that.
The default is required in the case the entity does not have an expected value (it is after all just a ‘string’ and you can not use a ‘string’ as a ‘number’,) or none at all.
The default is a safeguard to prevent the template output from erroring.
more details can be found in the etc etc…
sure, cool.
its just that this is not only about delimiters 
it can be if you want it to be, and then there is a very small and succinct example of the specific brackets we use.
I believe Petro also posted that several times, so lets find that and re-post it here
btw, on the subject of default, I truly dislike it, as it in fact creates a fake/false output… it might be good to lightly suggest reading up on availability_templates, which imho are a better way of preventing erroneous output. (albeit making the entity unavailable in the case of trouble, which many users dislike)
choices…