I was just trying to edit the tags on a Code Review question and for some reason I wasn't able to. I kept trying to add java-8 to a java question but nothing was happening. I'd click submit, the page would load and then my edit just wasn't there. No new tag added, no sign I had edited at all.
After a bit, I realised that java-8 is just a synonym. So adding it to the post would be redundant and that must have prevented my edit. I went back to see how I missed the information, and this is what the edit looked like:
Admittedly I should have looked into that tag wiki as the description said, however nothing at all indicated that this was a synonym that was pointless to tag with. Nor did I receive any feedback when I clicked the submit edit button. I do think you should be shown the synonym when you search, but some indication of what it is would be better. Even just adding a line over the tag excerpt like "synonym of java" would have told me what was happening rather than having to open the wiki to understand.