The username of the content's creator you mean, right? In the condition I tried with "Simon Szabolcs" with no success.
If this author filtering will not work out for me, please provide an example rule to filter for preachit contents that have "Simon Szabolcs" as their author.
I contacted the preachit plugin's creator, he said:
I'm not sure that there is anything to fix in the plugin. The author is returned as the Preachers name. This is correct for the post data. It may be the user filter on the rules only works if you use the username for the Joomla user.
There are plenty of different options in the rules section. I don't know how or where the rules activated, but it may be that you can get this to work by using the regular expression filter or one of the terms filters.