I'm sorry if you find it 'paternalistic', but bearing in mind you write, and I think sell, some documentation on SME if staggers me that you don't know more about how SME works, and that causes you to go running round doing stuff that is unnecessary because you haven't read enough or asked the right questions.
The way to install on SME is via the contribs. If you want to try other methods then you are on your own.
The guides are:
https://wiki.contribs.org/Software_Collections:MySQL55https://wiki.contribs.org/Software_Collections:MySQL571. Does it work or does it not work
2. Is the wiki correct or is it not correct
Do one small thing at a time, read up around the subject including bugs, describe exactly what you did, and don't go hacking about with stuff you don't understand.
Mysql 55
Links are there for reference. As you know we like to try and document as much as possible. If we didn't include that then someone else would probably ask why not. We can't win.
Duplicate entries. As I am not sure which DB you are referring I'm not sure if this relates to mysql57 or not. Have you checked the forums/bug tracker?
Usage - yes, it could, but equally it is in 'Command line' which should be fairly obvious. You have wiki access. You are free to revise if you want to.
LocalNetworking. You aren't reading very carefully. On the main wiki page it says:
config setprop mysql55-mysqld port 3307 LocalNetworkingOnly no
This does not expose the port via the firewall so is no more insecure than the stock Mysql.
On the pialasses page it says:
config setprop mysqld TCPPort 3306 access public status enabled LocalNetworkingOnly no
Note the 'access public' bit? That will tell SME to open a port on the firewall to allow access. That isn't in the SME wiki page.
Breach of security? The only security issues you will introduce are ones of your own making. Again, if you bothered reading the wiki and understanding SME more you would understand this (or at least ask the right questions)
Here is your starter on firewalling:
https://wiki.contribs.org/FirewallIf you read and digest that you will note the use of Allow/Deny hosts. Go right ahead and use them as they were designed.
Defining setups for every webapp is not practical. By all means go ahead and write a section on common usage for all the webapps out there, and whether or not they can use a socket. Personally I don't have the time to install and document them all. Do you?
Mysql57
Two templates for mysql57 my.cnf ? Because you haven't read enough to understand.
It is probably because there is a default one with the RH-SCLO rpm, but it uses different default paths to SME.
SME is NOT strict RH/CentOS and does not ALWAYS follow their conventions. There are entries in the SME contrib to configure mysql57 to run specifically on SME.
Hence playing about with stuff and making rash comments without really understanding things is not helpful. Get a SRPM. Check the code, See what it actually does.
So you then try this:
config setprop mysql57-mysqld bind-address 127.0.0.1
So where is that in the documentation? Have you checked if that is a db key? No. So you are thrashing around in the hope of solution instead of asking a sensible question (How do I limit access to the port, or How do I bind only to localhost), reading the documents, or looking a the installed templates.
Read above for 'Firewall' Then it may become obvious.
I fixed one of your typos but cannot see the other.
Webapps - as before.
I have modded the wiki pages a little. If you want to do more feel free.
I am happy to help, and indeed want to encourage, but you need to help yourself first.