See PHI1354. In the new Feed → Transaction Log interface, changes to settings (that is, user preferences like "Language" and "Time Format") render in an opaque way:

These also don't currently appear anywhere in the UI (e.g., there's no Settings → History).

Although one "fix" here would be to just remove them, there are a couple of cases where they're actually useful:

• When administrators change global settings, that's actually a meaningful change.
• When administrators change bot/mailing list settings, that could also be something that matters.

So the better fix is probably:

• Add a "Settings History" panel to Settings.
• Make all the edits render properly.

Then we'll get a useful history for global settings ("Who changed the default language for new users to Emoji?"), and for bots/mailing lists/users ("What was my old editor setting so I can go back to it?", although this use case doesn't seem terribly good), and a readable rendering in Transaction Log.