org-auto-align-tags

org-auto-align-tags is a variable defined in `org.el'.
Its value is

t

Documentation:
Non-nil keeps tags aligned when modifying headlines.
Some operations (i.e. demoting) change the length of a headline and
therefore shift the tags around. With this option turned on, after
each such operation the tags are again aligned to `org-tags-column'.

You can customize this variable.