I wanted to clarify my own opinion: I'm willing to call the right of reply a cultural difference to the extent that the right of reply consists solely of adding a link to the reply. This should go for everybody nowadays, including even established media; it should be sufficient for a television program to say "Go to our website for a link to blah's reply." with a link in a suitably prominent location.
The moment it goes into hosting the opinion, or required extensive verification, or just in general becoming difficult to do I no longer support it.
Real cultural differences exist and there are a variety of ethical decisions that can be made that aren't necessarily inherently good or bad; this is part of the reason my essay on ethics doesn't concern itself overmuch with trying to specify The One True Communications Law, because there isn't really a such. Since only the criticised entity has the right of reply, the "burden" of adding a provided link is minimal. (If just anybody could reply that would be burdensome.)
Now, if this were proposed in the United States I wouldn't support it for a second, because it doesn't fit into our culture at all. The United States practices a very chaotic form of free speech, even if some people don't like it, and that's our perogative. But again, as long as the right of reply is simply adding one link from one source, I don't think we could quite go to calling it unethical. Indeed, including a link to a rebuttal on a web site in many circles is considered simply common courtesy.
I see a lot of people commenting on it who have not read the proposal carefully. A link is explicitly mentioned as sufficient, so criticizing the current incarnation of the proposal based on the onus to host the reply is groundless. That's just one example of people over-estimating the amount of effort this proposal would require.
The fact is that while we have the right to free speech, we do have some corresponding responsibilities, and if a culture wants to make pointing to the criticized entity a responsibility of the speaker I don't see how the link alone is going to stifle speech. And given the actual content of the proposal, in addition to the fact this isn't even an official government proposal, just a zero-power council, I just can't find it within me to get too excited about this. (Note I explicitly disagree with much of what the author says in that post and a later post on the same subject; for instance I extremely strongly disagree that "weblogs" have to be mentioned specifically in the proposal, by name apparently, to affect them. I'm just quoting my source on the "no power" statement, since I am not intimately familiar with European politics.)
There is one more interesting point which is worth exploring, and that's who gets to define "criticism". For instance, by stating in the previous paragraph that I "explicitly disagree" with Harry Hatchet, does that mean I am "criticizing"? I would say it does not; I am merely disagreeing, without giving an reasons why, and in my book that does not constitute criticism, merely a statement of disagreement. If the bar for "criticism" is set too low, perhaps all the way down to mere "less then totally favorable mention", then this could once again become onerous. Granting a right of reply to someone because I refer to them as "practically perfect", as opposed to "perfect", is absurd. If the definition of "criticism" becomes unreasonable this falls apart.
So again, while I narrowly approve and seem to be going against the grain of the opinion of many people whom I normally agree with, the approval is very, very fragile and subject to many conditions.