For disclosure, it may not be a speedy fix that you may be wanting. It's nothing to do with Crossfire as this bug has been identified as occurring with all other sites in the network using the same editor (i.e., many sites). There is no new update since my previous reply. The issue is known and still being reviewed as to how to address. Since this is considered a bug, and it's isolated to specific usage of the size tag which is limited in usage, it will likely take some time. That it also involves a feature that is not exactly fully supported (which is why the option hasn't been on the toolbar for a while) as it doesn't scale well across multiple platforms, and is also part of a complex editor, doesn't help.

To note, you can still edit posts and signatures and still use the size tag. All that's happening is the What You See IS What You Get editor is not parsing the size tag properly in the preview mode. The tags and content are still there but are "hidden" in the preview due to the bug. You can edit around it and/or use the source button if you have some familiarity with HTML. Yes, it's not easy to update, but it's possible and not actually rejecting any content.