With the caveat that all jurisdictions are different, defamatory republication can take place at a number of levels. If 'publication' is defined by the receipt of the communication (and it is not in all places, notably I think the US looks at point of origin), then there is potential liability on the part of a) the original author, b) the publisher who disseminates the author's work, c) the company which provides a platform where the dissemination takes place, and d) users of that platform which cause the dissemination of the material further still. Which of those people one decides to sue is essentially a tactical matter - are you going to sue a facebook user who has caused nominal damage to your reputation by exposing perhaps one or two other people to the defamatory material (and there'd be substantial evidentiary hurdles with that, I'd imagine), or are you going to sue the publisher (e.g. the online news website) which has caused substantial damage by exposing thousands or millions of people to the defamatory material? If 'liking' a facebook post naturally brings it to the attention of others, then it's undoubtedly a republication, but the circumstances in which the damage would be anything other than nominal seem pretty limited. It's the same as communicating defamatory material that you read in the newspaper to someone in a private conversation - it's undoubtedly capable of being defamation (subject to certain qualifications, of course), it's just that, other than in exceptional circumstances (e.g. telling a prospective employer of the person you're defaming), it makes no tactical sense to focus on the individual rather than the newspaper from where they got the information in the first place.
Crucially, I also think it misses the point to consider 'liking' just in terms of republication, when it actually amounts to an original communication in itself. Not only does sharing the original material with others amount to a republication of that original material, a 'like' also provides some additional, potential defamatory content, in the same way that saying "I endorse this" would. This is most obvious in the case of public figures with large social media followings - if they were to 'like' something, they are not simply neutrally conveying the original defamation to a wider audience, but are effectively adding the weight of their own credibility to the defamatory material.
It's worth pointing out that the most obvious point of difference between the tort of defamation that is mostly being talked about in this thread, and the Swiss case mentioned in the OP, is that the latter appears to concern criminal defamation, and a 'fine'. The gist of tort is damage, which by its nature leads to a compensatory, not punitive, sanction. Criminal defamation is a whole different ball game from tortious defamation.