The cookbooksuggests to use DataTransformer tostrip_tags from input.

Isn't that violation of"Transforms a value between differentrepresentations"?

I mean, when u strip tags, it's not that representation of data changes – it's the data itself that gets changed. Stripping tags is a losing data procedure.

A cleaner way would be to use form event listener to change the data.

The example is almost right to use DataTransformer to change'<br>'s to"\n" and vice versa – almost, because the input could have both'<br>'s and"\n" – the original information, which should be where, would be lost as well.