We have rules regarding where swearing is ok - non-directed, mild swearing in private categories only which visitors can’t see (any TL0+ category iirc). You can see that policy in the DevForum Rules.
In the case of the activity page, this is a non-problem. Activity on private sections of the forum will not be displayed so long as the user lacks permissions to see that category. For example, if you are a Member, you will not be able to see any of a Regular’s Lounge activity at all. Stats will still show as expected however you will not be able to see content from sections you don’t have access to.
Whenever possible, you can always flag inappropriate content around the DevForums. If it’s not immediately clear what you’re flagging for (e.g. like an image’s alt text), use the Something Else option and specify your complaint. If it’s non-flaggable (e.g. an inappropriate link on someone’s profile), send a message to the Developer Engagement Team group to have it investigated.