For many years browsers could show visited links with a different color. Usually non-visited are blue and visited are something like purple.
It works this way also in Wikipedia, but when editing an article using VisualEditor, this is not always respected. I suspect that it is like this with articles that include an apostrophe (') in the title, but there may be other reasons.
By itself this issue is by no means high-priority, but it may point at an inconsistency between how the links are handled in VE and in the rendered page, and this inconsistency may cause other issues.