A few global editor settings are available for you (as the administrator) to configure for your community. To edit them, navigate to Customization -> Editor -> Settings in the AdminCP.
By default, in IPS 4.1 onwards, when a user pastes formatted content (that is, content copied from elsewhere that contains HTML formatting such as bold, italics etc.), a bar appears in the editor asking them if they would like to retain this formatting, or remove it and keep the plain text:
Some administrators prefer that no formatted content is posted, and the Paste Behavior setting allows you to control this.
Return Key Behavior
By default, when the user presses the return key, a new paragraph is started (and there's there's a space between the new line, and the line above), in common with many modern web apps.
However, some administrators prefer that when the return key is pressed, a simple line break occurs and the same paragraph continues (this is how IPB3 handled the return key, too). The Return Key Behavior setting allows you to control this.
When a post is submitted, the post parser strips out certain HTML tags, attributes and values that are potentially undesirable for security or visual reasons.
However, in some cases, you may want to alter this behavior and allow certain values through. The Advanced tab allows you to add exceptions for:
By default, other than certain 'known' CSS classnames that IPS4 needs for things such as quotes, classnames in elements will be stripped out. If you need to retain certain classnames for editor plugins or buttons, you can add them here.
Allowed iframe bases
By default, iframes are usually stripped from posts. However, if you have a need to allow them, you can add URLs here. If the URL of an iframe matches one listed, it will be allowed through the parser.
It goes almost without saying that you should be careful about what you add exceptions for on the Advanced tab. Allowing undesirable values through the post parser could lead to visual abnormalities, or worse, security issues.