ada-indent-align-comments

ada-indent-align-comments is a variable defined in `ada-mode.el'.
Its value is

t

Documentation:
Non-nil means align comments on previous line comments, if any.
If nil, indentation is calculated as usual.
Note that indentation is calculated only if `ada-indent-comment-as-code' is t.

For instance:
A := 1; -- A multi-line comment
-- aligned if `ada-indent-align-comments' is t

You can customize this variable.