From my own answer on WorldBuilding.SE to the question Is there a way to see my interactions with another user?:
There are no easy ways, but you can use the StackExchange Data Explorer (SEDE) to find these things. I made a few very simple queries with a few examples that I could remember at the top of my head. You can switch whether you are looking at the main site or the meta site in the upper right hand corner. Just copy the code and change the values for the Ids and usernames that interest you.
I just randomly chose Ids that I could find fast.
Comments where we cited each other
You can use this query. Just change the UserId and the name. The first UserId is my own and I am searching for a text that would look like "bladutchbla" when converted to lowercase text. This is to find interactions with the user L.Dutch. I am combining this with the search for comments by L.Dutch (the second Id is his) where he mentioned my name.
You can find your Id and that from other people by going to their profile and looking at the URL in your browsers address bar. For example my profile shows
https://worldbuilding.meta.stackexchange.com/users/28789/secespitus and the important part is 28789.
The link in the first column will automatically take you to the specific comment.
Answer I posted to a question from the other specific user
You can use this query. This time I used Mindwin's Id. The first Id should be your own (your answers) and the second from the person you are interested in (their question).
The link in the first column will take you to the answer.
Answer the other specific user posted to one of my questions
Just use the above query and switch the IDs.
Questions where me and another specific user both answered
You can use this query. I chose the Id from myself and L.Dutch again.
The link that you get as a result will take you to the question.
That should give you a start for your interactions with another user, especially about the "one person asks and the other one answers" part. Remember to change the site and to look at the IDs on each site. You have different IDs on different sites of the network and SEDE only allows you to search one specific site at once.
The links will also not work directly. You have to change the query and change "worldbuilding.stackexchange" to "stats.stackexchange".
Here is an example for this site ("stats.meta"):
Comments from one user under question from another user
I used your ID for the question giver (58675) and the ID from Glen_b as the person to comment (805). Just to be clear: the first ID you can see in the query is the person that is supposed to have written the comment. The second ID is the person that is supposed to have written the question.
I also changed the link-building part in the first line to say "stats.meta" to link directly to this meta site. The "Posts.PostTypeId" in the last line is the type of post that you are looking at. "1" means "question" and "2" means answer, so if you want to change this to look at cases where one person posted a comment to an answer of another you can change this PostTypeId when adapting the query.
I simply chose the IDs because the two of you interacted the way you want to look at here in this meta discussion. SEDE takes some time to update with each data dump, which I think is the reason that I couldn't find the specific comment by ordering the results according to the creation date, but you can see that the query works by clicking on the links and then looking at the person who wrote the comment and the person who wrote the question.