I could really use such software to improve my own writing.

Reason: I have always been struggling with the demarcation line between original and plagiarism. As a student of Greek and Latin history I personally recognize that all our supposedly 20th century orginal ideas have precedents in Roman, Greek and Egyptian times, and that we just mix and improve ideas of others, because that is how our brains treats partially remembered information. Since I am very active in engineering and know a lot about engineering history, I have seen a lot of 19th century inventions being re-patented as new, without barely any modification, and actually receive legally protected status.

But in my original field of study, 'law', nothing is really 'new', since law is an old field of study and every discussion position has been taken somewhere in some legal jurisdiction; sometimes, ever. At least, if you shop around and read a lot in your field you discover your in-originality very quickly. I always found 'plagiarism' a very fishy ill-defined concept since labeling something as 'original' by experts in a field, is usually based on a lack of knowledge by experts regarding the history of their field. (this was in an era before such software existed)

So is it just software verifying if you copy pasted a fragment of a document without a reference? How many languages and countries does it cross-verify? Can it check if a paragraph found elsewhere was rewritten and reused in your document (which is common practice even among 'phd level original creators'), or is it software that can check whether an idea is original (proving an idea is original, even a patented idea, is a very hard thing to do, especially with software, that's why it has to be arbitrarily decided by arbiters and judges with imperfect knowledge and 'common sense'). Then again, A.I. might one day attain the level of abstraction needed to judge this in a more objective manner.

The result of my insecurity about 'originality' is that I have been sitting on a drawer filled with 'supposedly' original ideas for years, avoiding academic publishing, believing that being perfect in my search for prior art is more important than communicating an idea and progressing in open discussion. This conflicts with my ambition of being an entrepreneur and just going for it. Blogging is of course something else.

Is the general argument valid that the hunt for plagiarism might lead to a stagnation in innovation?

To remedy such insecurity it would be nice to have a tool I can use myself to baseline if I am actually a plageriser or an original thinker, or if my ideas are worthy of being published (e.g. is it sufficient to quote a source not to be a plageriser, or, for academic publishing, do your ideas have to be 100% 'original', in all aspects as well? ), and if software can help me make that distinction, at least for some aspects of writing, it would be great.

We can go into a discussion about peer review as well, but, this is supposed to be a question, not an article.

So yes, where can I get such software, which one is a reference in its class and is it affordable for a private person?