The table that store upvote is named comment_like
and post_like
. Here, you have the vote’s unique id, the local user id that is linked to the it’s “global id”, the local post id which is also linked to it’s “global id”, the value of the vote (+/-1) and the date.
So votes are indeed totally not anonymous.
(and I run my server sinces less than a week, and the sum of entry in the two table is of 114 950 votes. Certainly enought for doing a bunch of analysis.)
Example of datas for the comment vote table (ids has been changed)
id | person_id | comment_id | post_id | score | published
-------+-----------+------------+---------+-------+----------------------------
1 | 10 | 3 | 61 | 1 | 2023-06-17 20:01:20.948684
2 | 34 | 1 | 22 | 1 | 2023-06-17 20:01:26.346783
3 | 12 | 2 | 54 | 1 | 2023-06-17 20:01:27.627144
4 | 20 | 7 | 91 | 1 | 2023-06-17 20:01:36.570636
Matrix use the term of “homeserver” too