The translator document uses the %...% convention for translation parameters:

I have %number% apples.

However, the Validation component uses the {{ ... }} (twig-like) syntax for translation parameters:

This value should at least be {{ minValue }} characters long.

This has confused some people already, especially when creating their own constraints:

• Should they follow the translation or validation conventions?
• The documentation follows the translation conventions, that seems inconsistent

I would suggest to have one standard for translation parameters and use that everywhere in the core framework.