You can use the listen to functionality. See documentation here: https://docs.mendix.com/refguide/listen-to-grid-source#1-introduction
The clicked ticket will be used as parameter for a dataview and you can then place the comments grid inside this dataview and retrieve over the association all comments on that ticket.
You can pass through 1 object to a page in a data view. This will be the page parameter. In this case I guess that Ticket and Comment are associated with a 1-* or 1-1 association. If 1-*, you can put a list view in the data view of Ticket has context as data source. Then select the correct association. If the association is 1-1 the idea is the same, but use a data view and not list view