I assume that there are many natural questions about various stats before and after the change of upvotes on questions from +5 to +10.

I can imagine people asking (to list some examples):

1. How many yearling badges were awarded on that day - compared to other days? (Similarly for other badges influenced by this.)

2. How has average score of questions changed after this. (Similar question for other stuff related to quality of posts. Of course, to see the actual data we'll have to wait at least a few weeks.)

3. How much has the reputation for users changed.

And so on - one can think of endless possibilities.

Would it be a reasonable idea to create a post on Meta Stack Exchange where queries related to this change would be collected?

I played around a bit with reputation before and after. (Of course, reputation cannot be calculated exactly from SEDE - there is daily repcap and other problems. But at least we can have uncapped reputation as an estimate.)

I have tried this: Estimated old and new reputation of a user (without offered bounties)

And than also some queries collecting data about users. It's possible that the query where I also subtract the offered bounties is more complicated than necessary, but I did not know a simple way to "add a column" with bounties to another CTE.

Estimated old and new reputation (without offered bounties) and Estimated old and new reputation

Of course, if we are interested only in reputation change and not in actual reputation, it suffices to count number of upvotes: data.stackexchange.com/math/query/1150477/…

Users with largest reputation change after question upvotes were changed from +5 to +10