In addition to enabling “open external links in a new tab” it would be great to have a way of differentiating between internal and external tabs other than to look at the information given on mouseover. Maybe a different colour or an icon like Wikipedia does?
All new external links will open in a new tab, so it does not apply to old links. There are also multiple ways to post a link, like wikipedia.com as you know, which would be harder to differentiate if I would use a different text tag. The other option is to put the website on one line, like so:
Which makes it immediately clear to everybody 
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I will consider adding the indication with a small icon later. So I will move this topic to feature requests. Please keep in mind to post 1 topic per feature here, no mixed issues or requests please 
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Thanks!!
Decision: external links opening in new tab is for now an acceptable and sufficient solution. Different colors and icons may be redundant.