There is 4 ways to insert a tag after inputting some text: comma, enter, selecting an auto-complete option, or de-focusing the widget. You can
Enter tags with space,
Cut and paste list of tags separated by comma and hit enter.
The only thing that seems to be consistent when this occurs is being logged in as the super administrator in the front end. To get the tags back, I must clear the cache. I hope to find a solution to this problem, as this is the most attractive, and most functional tags system for Joomla! 2.5 that I have tested, even despite this issue.
I will look at the issue and release a 2.6.4 soon.
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