Considered by whom? This is both an issue that has intrigued and bothered people since the dawn of photography and a still-emerging topic that is far from settled. So, in a larger sense, there's really no meaningful answer, just a series of opinions.
But, in a specific sense, there certainly can be an answer. The definition you've taken above has a very specific use — it's the definition to use for photos in the photo.net image database. It's a pretty good, well-thought through definition and could be used elsewhere, but questions over details (like the mask-based sharpening you mention) can only be done in a specific context.
The US-based National Press Photographer's Association has this in their code of ethics:
Editing should maintain the integrity
of the photographic images' content
and context. Do not manipulate images
or add or alter sound in any way that
can mislead viewers or misrepresent
and a more-specific "Statement of Principle" on Digital Manipulation, which says in part:
Accurate representation is the
benchmark of our profession. We
believe photojournalistic guidelines
for fair and accurate reporting should
be the criteria for judging what may
be done electronically to a
Similarly, the Canadian Association of Journalists, in their statement of principles and ethical guidelines, says:
Photojournalists are responsible for
the integrity of their images. We will
not alter images so that they mislead
the public. We will explain in the
photo caption if a photograph has been
staged. We will label altered images
as photo illustrations.
Fpr both journalistic associations, the focus is on intent, and technical details aren't mentioned at all. It's probably fair to say that this is a far less strict standard than photo.net has, and, subjectively, that seems reasonable given the context. Note photo.net's reasons for their standards: photos in that database are intended to help others learn, and it is helpful to know whether or not a high degree of post-processing was required.
If you're entering a contest, that contest should explain their rules clearly. For example, the 2010 National Geographic Photography Contest has a statement including a list of okay and not-okay. This is summed-up as:
Please do not digitally enhance or
alter your photographs (beyond the
basics needed to achieve realistic
color balance and sharpness). If you
have digitally added or removed
anything, please don't submit the
shot. We look at every photo to see if
it's authentic, and if we find that
yours is in any way deceptive, we'll
For artistic and personal work, there's unlikely to be any expectation that your image not be manipulated, unless you create one — in which case, you have the opportunity to be as clear as you like about your process, and your views on photographic integrity.