It's only an "issue" to the extent that someone who is not familiar with the protocol might be misled by it. After 4 years running an exchange, one would hope that Gox would have someone familiar enough with the protocol to avoid this, but I guess not.
This is known design "issue", but it's a part of the protocol and thus not a bug which must be fixed. Bitcoin has many odd facets and all of them must be understood by anyone making bitcoin software.
It does sound like a bug in Bitcoin, and it's one that people have to specifically work around. It does not sound deadly, but nor does it sound ideal. And it does seem likely that someone figured out that Gox was doing what they were doing and exploited it, the question being to what extent.
But it is interesting evaluating the commentary given that people who have a vested interest in Bitcoin will naturally have a very strong reason to defend the protocol and fundamentals (the linked submission even encourages readers to go buy into the hype at a "huge discount"). This is something you see on equity trading boards, the guy deep underwater on the penny stock loudly defending all fundamentals of his choice.
> If you need a quick answer: there’s no bug in the Bitcoin itself.
> Is it a design issue in Bitcoin to allow slight changes in the transactions? Yes, probably is.