Generally Google is not paying any attention to the keywords meta tags anyway, so it's not really an advantage to duplicate them.Only thing If the meta description is duplicated, Then surely your website will be penalised by search engines.
Google does not even read the meta keywords tag so there is no advantage of having one.
If you duplicate the meta description tag on different pages then it will not look good, as Google often takes the meta description as the snippet in the SERPs. You would be at a disadvantage of having duplicate meta descriptions as they should describe in a sentence or two the content of the page. I would say that it is unlikely to lead to a penalty though.
Ah. The statement on Google is, of course, correct. They have long ignored the keyword tag!
However, the statement saying 'search engines' is always interesting. If you mean Google and Bing then having duplicate keyword tags is just sloppy and unneeded 'code-bloat'!
But 'other search engines' can mean search engines that do use the keyword tag. Baidu (for example) reads keywords in Pinying and will penalise for incorrect usage.
Then think about Naver which works in a totally different way to all other search vehicles.
So, seeing this is General Search Engine marketing issues - I don't see the World in a Google only light. Indeed, where I am based - I don't see Google as a major search engine at all in certain countries!
Strange but true - Google may control your internet world but not the whole internet world and, in some countries, barely scrapes the surface in terms of usage.
So, while optimising for Google keyword tags are a useless entity (apart from perhaps reminding content providers what terms on a page you are trying to concentrate on) - in the wider World where Google isn't generally used - they may have some beneficial use.