In the yearbook Jämten 1987 (ed. Sten Rentzhog) there was a theme, Te skriiv jämtska ('To Write Jamtlandic'; p. 166—188) on Jamtlandic. In the theme there are eight contributors writing an article each, where two stand out (at least in the context of the principles of creating an orthography): The young enthusiast Bo Oscarsson (1947-) who was (formally) an amateur in linguistics, and the veteran Vidar Reinhammar (1925—2000) who was one of the most prominent dialectologists in Sweden.
In Oscarsson's contribution, Jamskan och stavningen ('Jamtlandic and the Spelling'), it's argued against a phonetic spelling. The contributor wants an orthography which is consistent with other North Germanic languages' orthographies, which aren't based on phonetic principles. That is, he desires an orthography within the boundaries of the North Germanic tradition. He argues against using innovative, special letters to denote special sounds. Though not explicitly stated, he probably also wants a unified orthography for jamtlandic.
It should be noted here that Oscarsson had been a follower of the phonetic principle, but that after reading the work by the early pioneer Erik "Äcke" Olsson (1860—1916) who went from a phonetic spelling to a semi-etymological one, he changed his mind in 1976.
Reinhammar's contribution Jamska eller jämtmål? ('"Jamska" or Jamtlandic Dialect?', referring whether there's a Jamtlandic language or merely a set of similar dialects), which follows immediately after Oscarsson's though probably not written as a direct response, argues against a unified Jamtlandic orthography. His main argument is that the dialects are too different and that the status of the dialects which are not compatible with the unified orthography will be lowered and eventually extinct, just like how Jamtlandic has been lowered in status against Swedish. Reinhammar wants a diversity of dialects for which the writers can use whatever orthography they want. A unified orthography will in the end, he argues, destroy the dialects.
There's a fundamental difference between the two which explains why their views are different. This is how I interpret things. Oscarsson is a Jamtlandic nationalist, and it's the fate of the Jamtlandic language as a whole which is important. Reinhammar, being a dialectologist who doesn't acknowledge any Jamtlandic language, focuses on the dialects and argues that Jamtlandic is nothing more than the sum of the dialects labelled as Jamtlandic.
Boiling it all down, the "debate" is mainly one between a young, passionate patriot versus an old, cool scientist. They simple speak different languages, so to say. Their goals aren't the same, so their arguments become incompatible.
Personally, I feel that I support Oscarsson, though one needs to take it cool. Passion with scientific support is the model I follow in my own work. Oscarsson had the ambition, but unfortunately he didn't have the ability to employ his etymological principles in all aspects of the work on creating an orthography, and he compromised to much. (See below in the aftermath paragraph.) Oscarsson's main contribution to Jamtlandic has been his enthusiasm, and it was this that led me into the field a decade ago. But needless to say, it's the work of Reinhammar (and other dialectologists) which have the greatest relevance to me today. I hardly use Oscarsson's dictionary anymore, and it has become evident to me that he's too involved in "mammon". (I have suggested that the dictionary should be freely available on the internet as a pdf document, but this isn't possible due to legal contracts and copyright issues with the publisher Jengel.)
Aftermath. In the mid 90's, the document Vägledning för stavning av jamska ('Guide to the Spelling of Jamtlandic') was made public as the outcome of the work of Akademien för jamska ('Academy of Jamtlandic') consisting of Bo Oscarsson, Bodil Bergner and Berta Magnusson. It's a semi-etymological orthography and semi-unified, i.e., it doesn't follow either of Oscarsson or Reinhammar in their Jämten 1987 contributions. I have been speaking with Oscarsson about this and he tells me that the reason is that he had to compromise. Interestingly, only Bo Oscarsson seems to follow the guide. Berta Magnusson, who is perhaps the most important writer in Jamtlandic who often publishes material for the local press, doesn't seem to follow her own guide today.
The current most important literary work with an orthography supposedly based on the guide is Nagur bibelteksta på jamska ('Some Bible Texts in Jamtlandic'). Unfortunately, since the guide is merely a "guide", the various contributors to the translations don't follow the proposed spelling.