My guess is, probably because 'rarely' is a more accurate translation than 'seldom'. You see this in other languages too. In French, 'agréable' is more accurately translated as 'nice', and not 'agreeable'.
If anyone knows more, please feel free to correct me!
maybe..... I think "seldom" perhaps means a little more rare than "rarely" (MAYBE), but they very much mean the same thing in this example.
The important rule for Swedish here is that the verb goes in second place in the sentence. So if you start a sentence with the subject, you must have the verb next, and then it will only be possible to have the adverb after the verb.
I wrote some more about word order in general here: https://www.duolingo.com/comment/8970470
No, usually the adverb comes after the verb, but there are exceptions. Which did you have in mind?
I meant that in English the adverb usually goes before the verb, right? "I often go home", "I usually sit her", but not "she rarely is here". Why is that?
I think it actually has to do with the verb phrases. Like you can't split "go home" or "sit here" because going home or sitting here is a single action phrase, so the sentences are either "I often go home" or "I go home often", but not "I go often home".
Whereas in "she is here", "is" the entire action (her state of being), and "here" is just a description so "is" and "here" are separate clauses and can be separated ie "she is rarely here". FWIW I think "she rarely is here" is also acceptable grammatically, just not in common usage so it sounds awkward.
Ah, I can’t answer for English, but in Swedish it usually comes afterwards.
I think it is because of the verb 'to be', because you can place 'rarely' before an other verb: 'I rarely go to school', while you don't place an adverb before 'to be': 'I usually am here', but you do say 'I am usually here'.