In the field of applied math where a paper has been accepted for a conference presentation (talk), is it common for the ordering of the authors to be changed for a proceeding that entails thereafter?
Here is a quite frequently occurring extreme case which may help you evaluate your own situation:
As @JonCuster also mentioned in their comment, there is always plenty of time between the abstract submission and the presentation itself, and the work typically evolves a lot during that period. Imagine it evolved such that new collaborators were added. Adding new names in there may change the list of authorship a lot. Imagine also that you actually submitted the manuscript by the time you present it, of course with the co-authors on it. In the conference, strictly adhering to the list of authors submitted in the abstract would mean removing your new co-authors, which should be out of question as it is best practice to give them credit as co-authors of your work. Thus, the list of authors can definitely change during the actual presentation as one is usually entitled to also present improvements to one's work. Whether it is common in your field, I don't know, but my guess would be that it is not too rare.
My experience is it is no big deal provided the papers are not set for publishing. I would consider it similar to any other minor edit to the paper. If it can be done logistically fine. If it requires review, and authors wouldn't, not fine.
In general it is not possible to change the order of authorship once a piece of work is accepted at a conference/journal etc. This is for several reasons:
- Authors should think about the order of the authors before they submit and if the work contributions afterwards change then this work is normally not part of the submission and what counts is what was submitted on not if further work was put into it later.
- The reluctance to change authorships also comes from the fact that sometimes authors try to get their name of a fraudulent paper and this is something journals want to avoid at all.
If you can prove exceptional circumstances and all other authors agree (in writting) you might have a change by writing to who ever is in charge. But this should only be done if really necessary and you have a really good reason.