Yes, a Level assignment or tag would be helpful to the community documentation. Perhaps a color-coded tag or a 1 through 5 Level assigment for each page might be useful. I don't think such a feature is built into the wiki engine, so we would have to rely on tags or some other annotation method.
As an example:
Level 1 Beginner Level. Basic point and click instructions using the current graphical interface. Point the mouse to a menu and select an option to activate a feature.
Level 2 Medium Level. You might have to dig through tabs or used advanced features within a dialog box to find a configuration item. Changing such an item might effect other aspects of system operation, so be aware of that. Changing themes, colors, or resolution would be an example.
Level 3 Advanced Level. You should know how to open a terminal window and type simple commands. Understand case-sensitivity and correct typing are required. Must know how to open a manual page for a given command: *man cp* Know how to search google or the forums for answers to common or obscure problems as they arise.
Level 4 Old Hat Level. You can install and remove packages with ease at the command line, You know the linux file system structure like your neighborhood streets--including finding your way home when you get lost. You know where log files are and how to read them when things break. You know how to fix things and you acknowledge that you get to keep the pieces when you break things. It's your system. It continues to be your system even after you break it. You acknowledge that it may take time and patience to fix things. It may be more time than you have.
Level 5 Guru Level. Your bean count is in triple digits and you get annoyed easily. But you know how to compile a kernel and are aware that everything in linux is fixable.
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Regarding Iptables
There should be a paragraph right up front that says something to the effect:
*iptables* is an administrative tool for filtering packets and is used as part of a Network Address Translation (NAT) system. You need to be familiar with the TCP/IP protocol, the general workings of the networking framework (or "stack" as it is sometimes called) and how data packets are built, sent, read, and processed. You create policies (or rules) for how to handle certain packets. *iptables* is generally used for blocking unwanted websites or spam or other undesirable web traffic, but it can be used for sophisticated traffic handling. This is a Level 4 topic.
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The above paragraph would have several links to documentation pages for the above prerequisites that were called out. For instance for Internet Protocol (IP) you could use this, but your eyes would glaze over. So perhaps you could link this.
Linux becomes much easier to learn when you appreciate how many layers are used to build it. Then it simply becomes a matter of time to read about all of the layers. A lot of this stuff is 30 years old, so if you aren't familiar with these concepts, you have 30 years of reading to catch up.