There is two silver badge for editing posts:
Strunk & White: Edit 80 posts.
Archaeologist: Edit 100 posts that were inactive for 6 months.
But I think it's a little bit strange that Archaeologist has two stronger conditions than the other one.
It's common that if two badge have the same value, there is some trade off between their options. So I think if Archaeologist has the additional condition on the period of activity, it's better to reduce the number of posts required to edit.
There are also several other badges that are strictly easier than other badges of the same category.
A common theme is, perhaps it's not without exception though but anyway it is the case in this instance, badges that were introduced later can be strictly harder than existing ones.
I do not find it all that counterintuitive: there are a couple of easier badges for beginners and if you want more, the tasks get harder.
Now, would Archaeologist only require, say, 50 edits, I would not see anything wrong with it either. Yet, I do not see a reason to change the criteria now after the badges were around for years. Mainly as I do not really see what problem there is to be solved, and also as to actually get rid of this phenomenon many changes would be needed.
