You should be able to edit xml files as well, make sure the tags are properly opened and closed, if it is a invalid xml then it won't let you save the file.
On further investigation, the AA Workspace doesn't handle comments as expected. For instance:
This is "Valid" in the AA Workspace:
This is a comment,
Whereas this is not valid:
While most XML formatters (and indeed, the formatter used by the view in the AA workspace) identify the second example above as valid, AA does not.
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