This issue is happening because you typed out "age of" and then clicked "age-of-empires-2" from the suggestion drop down that shows up. When you do that it adds "age-of-empires-2", but it doesn't remove the "age of" tags that you included. I'm assuming this is expected behaviour, since it lets you add multiple tags at once. In order to avoid this issue, ...
Yep, I was right.
Wildcarding tags returns a maximum of 20 tags
Searching for [*tag*] is the same as favouriting [*tag*], so I performed a few searches and compared the results.
This is what I searched. I wasn't particularly interested in the results, just in generating the maximum amount of tags possible:
To get there, start at the questions page.
Down the right hand side, you'll see your "Favorite Tags" list. Click "edit" and make sure you have some tags selected.
Then click "advanced tag subscriptions" and then scroll aaaaaallll the way down the page. In the lower right hand corner will be the RSS link.
This one is mine, for instance: