I’m not sure why you replied to an earlier post…
Are you trying to argue that this case isn’t loshon hora at all or are you arguing that it is loshon hora but it’s allowed l’toeles and this would be considered l’toeles?
That depends which case you’re talking about. If someone would do a direct price comparison in a case where neither store is violating halacha, I don’t think it’s l”h to begin with. If the higher price is a violation of halacha, it is muttar l’toeles.
The point is that when you post something online it stays there forever. That is why it may have a different din.
That should not matter, since it’s clear that the information is from some time ago and may have changed.
The reason online discussion can be worse is because if inherently bad information is posted, there may be people reading it for whom it may not be l’toeles. The question would be if the fact that so many more people will be warned is itself a toeles.
Also, subjective reviews are a bigger problem, because you don’t really know the tastes of the reviewer and whether it applies to you.
Reading negative reviews is a further problem, because you often don’t know that the information is even being given honestly.