Does the Kobold effect stay or can you reduce it?

That’s a little vague and can be misinterpreted.

What I mean is, if I get hit by one pie, without being transformed, is there a way to reduce the amount of corruption or do I only get a few strikes?

If you’ve just taken the one pie, you will be 2% kobold, 98% original species. The next pie will make you 4% kobold and 96% original. The way the species transformations work is that game tracks species transformation in a buffer, so you can “push”, say, the Kobold transformation off the bottom of the stack by getting new transformations. This is rather like the way Nimin and CoC works if I’ve got it right.

Currently the only other transformation is the bovine one, so you could use that to nullify the Kobold one - at the expense of becoming bovine. One bovine exposure on top of that pie would make you 2% bovine, 2% kobold and 96% original. Both the percentage and the how recent the effect occured will determine what physical transformations happen.

At some future point when the planned magic items shop is built out, you’ll be able to purchase potions (at some expense) to restore your original species.

I see. Also, why does bovine make you shorter? Shortness isn’t really a major trait in bovines like kobolds, right?

When the transformation starts the engine picks a final target height from the range available for the new species. So either you are transforming into a below average height bovine, or it’s a bug.