There's currently no way (at least that I could figure out) of using an "advanced" search.

You can easily search by user by typing the user name and adding "@" at the end.
You can search by comment by just typing free text.

However there's no way to combine the two.

Past a certain team size and number of changesets, it makes searching really hard to use.

I would expect:
* "user@" to find all changes by "user"
* "feature" to find all changes containing "feature" in their comment
* "user@ feature" to find all the changes by "user" that contain "feature" in their comment
* "user@ creation>2022/11/1" to find all changes by "user" since November First 2022.