As per the title, the YML validator for Pipelines (https://bitbucket-pipelines.prod.public.atl-paas.net/validator) does not show any syntax errors for yml anchors.
This is highlighted in this example public repository: https://bitbucket.org/rtest123/anchor-indentation/addon/pipelines/home#!
Added by Theodora Boudale :
I would also like to add that sometimes a YML anchor also breaks validation in other parts of the yml file.
Above^ the lack of a space between '-' and 'step' for the branch named 'anchor', is not indicated by the validator.