Enlighter may throw some notifications/warnings/error on the top of the Enlighter settings page - these notifications are indicating some possible issues with your hosting environment or WordPress installation/configuration any should taken serious!
The use_balanceTags options is a legacy feature of WordPress core to "fix" invalid/bad xhtml syntax - it may sound helpful but in real-world-scenarios in causes more issues as it resolves - especially the Gutenberg or Classic Editor produces bullet-proofed xhtml markup and its not needed anymore it has been removed from WordPress v2.
In case you have a very "old" (updated) WordPress installation this feature might be still active and causes random content inserted into Enlighter sourcecode.
Reference: https://core.trac.wordpress.org/changeset/3223
Notice: This setting is not longer available within the standard WordPress settings menu. You have to open the raw settings editor on <yoursite>/wp-admin/options.php to alter the option (or within WordPress wp_options database table).
WordPress automatically recognizes smiley sequences like :) or :( and transforms them into images. Due to an error within the parsing function in WordPress, this feature also transforms these sequences within sourcecode - especially pre and code tags which also affects Enlighter. It causes html fragments to be inserted into the codeblock. To avoid such issues there is currently only one workaround: disable smileys globally.
A ticket for WordPress Core has been created including a fix which will maybe released soon.
Notice: This setting is not available within the standard WordPress settings menu. You have to open the raw settings editor on <yoursite>/wp-admin/options.php to alter the option (or within WordPress wp_options database table).
Crayon Syntax Highlighter won't work together with Enlighter. In case you use both in parallel, the Crayon content parser will take over all Enlighter <pre> code elements and disables the Enlighter highlighting. You have to choose between the plugins.
Enlighter requires a writable cache directory in wp-content/plugins/enlighter/cache/ to store custom themes and the editor styles. In case the directory is not writable please change the directory permission to 0744 or 0777 depending on your hosting environment. Otherwise the Theme-Customizer as well as the Visual Editor Plugns won't work!
In case you may have uploaded the plugin manually this error will be thrown: the enlighter/ directory name is mandatory - normally the plugin will be located in wp-content/plugins/enlighter/. You have to change the plugin location - otherwise Enlighter wont't work!