I have issues I could use your help in analysing the idiom usage, and the correct grammatical terminology to describe them, as well as the terminology of the corrections.
The use of arguably within the context of a modifying adjective seems to me to have no value.
Example: He is arguably the preeminent scholar in this subject.
In my opinion the correct manner in which to describe this person could, as an example, be one of the following:
1.) He is among the preeminent scholars in this subject
2.) He could legitimately claim to be the preeminent scholar in this subject.
3.) His preeminece as a scholar in this subject is widely known.
What bugs me the most about using this word as a modifier is that it implys an arguement!
The second regretable "New Idiom" is the proliferation into the American venacilar of the two word phrase, "Went Missing"
This is now standard grammar for all media idioms when describing the situation of a missing person.
"Jane Doe went missing today and after an all day search the police still don't have any clues as to her she is."
When did this begin? How? do you have any impirical information or dates on this rediculous grammatical phenomena?
It is used as casualy as the word is meant to be used, in contextual situations that are embarrasing to listen to or watch!
"Where is your sister Jane today?"
" Oh, I think she went shopping. No. Wait. I remeber now. Duh, she went missing!"
"Oh I see, well, wy don't we go to Starbucks and see if she is there."
HOW DID THIS START?? WHEN?
If you could help me grammaticaly describe these issues I would be most appreciative.
Also, feel free to correct anything I have written here today.
The first sounds OK to me; it means that others may disagree, but he is one of the serious candidates for it. Of your examples, 1) could be used, but 2) suggests to me that he is probably recognised as such, and 3) takes it further into the realm of an established fact.