I think I’d describe the problem case (which I think you are most concerned about) as “unexpected deletion”. I think it’s ok for the deletion to be automatic, the default action, and ‘silent’ - mainly because if it wasn’t then “the problem with inexperienced users and placeholders” would instead be the creation of a permanent shadow taxonomy full of things like “stinky blue flowers”, “horrible stinging weed”, “scary lizard”, and “big tree” - and the whole point of placeholders is to be a temporary reference pending insertion into the Official Taxonomy.
The discussion about new species isn’t going to have gaps, because as soon as you use that placeholder in a comment or observation note it’s going to persist until you edit or delete that yourself.
Like this: https://inaturalist.ala.org.au/observations/106762973
Or this: https://inaturalist.ala.org.au/observations/229448264
So if we’ve got consensus now that “Coarse IDs Are Good”, and want to move on to “How can we improve the use of placeholders?”, then the questions I’d be asking are along the lines of:
- who do we need to educate?
- what do we need to explain to them?
- where and how is it most productive to explain it?
Because practical feature requests along those lines seem like something you could make happen, and might be a lot more enjoyable to pursue than dying on the hill where placeholders here mean something different to what they do in every other related use.