When we have a Project Key with underscore, the Activity Panel of this project doesn't show anything.

Steps to replicate:

• Create a new project with the Name Project X and the Key P_X;
• Create a new bug for this project with the summary abcd;
• Go back to the Project X Summary;
• Look the Activity Stream: it will show "No activity was found" (attached image)

Expected behavior:

• Create a new project with the Name Project Y and the Key PY;
• Create a new bug for this project with the summary efgh;
• Go back to the Project Y Summary;
• Look the Activity Stream: it will show the activity

I've looked into the logs of my DB Trace, looks like the query for this search changes the underscore for a blank space. Of course, it brings nothing back.

As per the official JIRA documentation the following is said about using _ in project keys:
Do not use ".", "-", or "_" Avoid using the dot (.) character (i.e. dot/period/full-stop), as the CreateOrCommentHandler currently fails to add comments to existing issues if the project key contains a dot (.) — see JRA-23180. Avoid using the dash (-) character, as this character is inserted automatically after the regular expression and before the issue ID number. Avoid using the underscore (_) character as there is a current bug in JIRA 5.x that the activity streams will not work for project keys using underscores — see JRA-27967.