The documents containing long lines can affect performance when opened in the text editor. If you choose to present the document with line wrap and is an XML document some of the features will be affected:
The editor uses a Monospaced font.
You cannot set font styles from Editor+Colors.
→ +Automatic validation is disabled.
Automatic spell checking is disabled.
XPath field is disabled in the Find/Replace dialog.
Less precise localization for executed XPaths. The XPath executions use SAX sources for smaller memory footprint.
The last two restrictions are valid only for XML documents.