I have been using Jira for a very long time now. I first came across it while contributing to Apache projects in 2006. I find the search features of Jira to be remarkably clumsy and inadequate. Nevertheless, very recently I learnt to solve a common problem of mine. Let us say, I know a user named `jdoe` has commented about a specific topic in some Jira ticket. How do I find that ticket? Here is the search filter for it:

    issueFunction in commented("by jdoe") and comment ~ "hello"

The above example would search all comments by user `jdoe` that contains the string `"hello"`. However one limitation of this solution is that the `issueFunction` field is provided by ScriptRunner for Jira, so you need this app to be available on your Jira for this solution to work.