This does not really matter in this discussion, but AFAIK Tchaikovsky in Russian is a name used for a male person, whereas the female form would be Tchaikovskaya. So your use of the pronoun "her" in your example confuses the matter.

The question is flawed. IF is a journal-level metric, not an article-level metric. Even as a metric for journals, it has come under serious criticism, as a simple Google search will show. E.g.: editage.com/insights/…

Is this your first mathematical paper? Is there any chance that it simply doesn't fulfil the formal standards that an editor would apply to a submission and therefore got rejected for formal, rather than scientific reasons?

When I write scientific code to test my theoretical results or to implement a method I am studying, I become, for all intents and purposes, a developer. Therefore all the arguments from the related StackOverflow question come into play, which was overwhelmingly answered with 'yes'.

I want to thank everyone for the comments and will accept this answer based on the majority vote. For the record, I ended up taking the free karma and submitted the report as it was, without any comments to the editor.

I think the results aren't big enough to warrant re-proving in a second publication.

@Mindwin Yes, I do.

Note that I didn't consider "asking" for co-authorship, but merely "offering" to the author to contact me, which I feel does make a difference. Anyway, it seems your view has the majority behind it and seems to be the way to go. It irks me not to get credit for a contribution, but perhaps this is something one has to get used to when reviewing.