If you are trying to query on a comment made by a specific user this capability does not exist natively in JQL. You would need to consider an add-on such as Scriptrunner.
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Welcome to community and congratulations on making your first post/question! :)
Unfortunately it is hard to understand what you would like to achieve. I guess you want to get some results (maybe search?) based on comment? or maybe last commented ticket?
Could you please clarify?
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