It doesn't do things on its own. You probably weren't paying enough attention to what you were doing. Review the import dialog and whether there's a metadata template, and compare what's shown in the Keywording panel's Enter Keywords view with its Will Export view.
With no metadata template enabled, it turned "11 > 2018, 2018" into "2018, 2018 < 11 < 2007 < DATE".
The worst part about this is that the "autocorrect" happens after you've finished with the keyword entry so you can't correct it. I don't mind suggestions but changing the keywords AFTER I've pressed enter is pretty annoying. Lr playing God and thinking it knows what is best.
After turning of "autocorrect", now I have to type the entry meta data entry in.
So either Lr does its own thing with keywords or I enter them all in manually. How fucked is that.
I suspect the problem here is it looks for "11" and finds it someplace in my keyword tree which means that the keyword autocorrection is broken in a pretty significant way: it gets confused by duplicate/already existing names that are elsewhere in your keyword tree.
Sorry, I lie.
With "Autocomplete text in keyword Tags Field" cleared (and restarted after) plus "Offer suggestions ..." from the Metadata/Catalog Settings cleared, it still gave me rubbish extras in my keyword list when I use a metadata preset. Fuckers.
To add insult to injury, it is not possible for me to fix these fuckups by Lr though editing keywords in the keyword window. I've got to manually fix them by editing the keyword list.
Does the engineer responsible for this crap read LuLa by any chance?