No, the WebDAV server is only started manually. See Settings -> WebDAV server.

This was required in earlier versions of iOS to be able to start the WebDAV server and bind it to the local Wifi ip address. 

I need to check if setting UIRequiresPersistentWiFi is still required in the latest version of iOS.

I can see how the system prompt that is shown in Airplane mode might be misleading.

In order for the WebDAV server to work, Textastic sets "UIRequiresPersistentWiFi" to YES in its Info.plist file.

This makes sure that a Wifi connection is enabled if possible. If you are in Airplane mode, this results in a system popup that asks you to connect to a Wifi network. You can just close that.

Textastic doesn't actually connect to the internet when you start it. Connections are only started when you connect to a remote server.

You can read more about UIRequiresPersistentWiFi in Apple's developer documenation at: https://developer.apple.com/documentation/bundleresources/information-property-list/uirequirespersistentwif

Currently, these files are not supported in Textastic.

Textastic can read .sublime-syntax, .tmPreferences, and .tmLanguage files from custom syntax definitions.

All code editor settings are available in the UI under Settings -> Code Editor.

Good idea. The ability to search the list of syntax definition would be nice to have.

Thanks a lot for the bug report! I can reproduce the issue on my iPhone. The syntax definition is actually changed, but that change is not reflected in "Properties" view. I'll fix it in the next update.

Do you mean when editing a file on iPhone? 

Great idea!