When machine translation is available, link adaptation works almost like magic - the translator has to change very little (even if the MT is bad!)
But when machine translation is not available, then all the links' targets are adapted, but the links' text is written in the source language and must be changed. This is inconvenient, because deleting the source text may eliminate the link. The user can, for example, carefully write the translate link text in the middle of the link and then remove the source text, but that is really uncomfortable.
It becomes even worse when the languages have different directions (English to Arabic or Arabic to English): All the text is in a different direction and the cursor moves very strangely. (I'm inclined to think that the default should be not to paste the source text at all in this case, though user testing may prove differently.)
So there must be a solution that lets the users enjoy link adaptation without having to do weird things in the translation area.
One thing I can think of is to have a new tool card in the tools sidebar that would show a list of available adapted links. Selecting text in the translation area and clicking a list item will make it a link.
The designers may think about something better.
Related issue: T90243.