If you place the cursor after the last character of a link and start typing then your text becomes part of the displayed text for that link: [[Fish]] → [[Fish|Fish and chips]] rather than the inte.nded [[Fish]] and chips or [[Fish and chips]] which would be expected from a WYSIWYG editor (even if it isn't what is wanted).
There is no way to edit part of a link at all, the only way around it is to unlink the whole phrase and relink the part you want linked.
This is not usually a problem, as you can work around by starting from after the space after the link.
However, this is counter intuitive if you want to add punctuation after the link (add it after the space, delete the space, add space after the punctuation). It also means it is impossible to add unlinked text when the link ends the line, as happens often on disambiguation pages. For example try adding context to the links at Mandi#People. Apparently a workaround is to insert a line break, add the text and then delete the line break. I've not tested this myself though
It is possible this is the same as bug 50945 but I don't think it is.