I fully agree to @macgirvin because currently redaktor supports an url array as well.
I also have to say that it is pretty frustrating for another AP implementor that Mastodon does not care to become AP “conformant” -
The spec clearly says which things are “Functional” (can’t be an array) which means that other properties like url should be supported.
In terms of url the caption says it explicitly “Identifies one or more links to representations of the object” !
In some implementations it is just an issue of the UI. It could simply map an array or Collection to <ul> and OrderedCollection to <ol> and then add some CSS …
However:
Personally I disagree that it is different from url –
I would clearly go with url !
The rel (relation) property in a Link is where we should specify such link relations !
E.g.: For redaktor rel="me" does the trick to lookup other “profiles” (but the protocol isn’t clear at this point)
or How about specifying alsoKnownAs as a link relation ?
please let me add
I don’t have time to recheck every platform again and see which ones work and which don’t
exactly the same. This is why I don’t care anymore while I am building a generic AP conformant server and client/UI …
I will have a look in the end if/how we can satisfy the limits of others (or if maybe not).
Most important : The computer says this is the first time that “rhiaro” posted here.
This is awesome. 
Yay. Hooray.