TRichView is a well-featured TRichEdit alternative that works well with Addict 3 and Addict 4.
More info: http://www.trichview.com

The TRichView author has recently update the Addict / TRichView Parser to supply better Addict 4 support - you can grab it from:

http://www.trichview.com/resources/adrv3/adrv3.zip

It works for both Addict 3 and Addict 4 - and includes a demo.