I wrote a real simple plugin for my site for word replacement. I just put the words into an array, the replacements into an array (they are all links for the moderators to use) and then do a simple str_ireplace. It works on 3.6 and 3.7. I would think that is the way most of the modifications for word replacement would work. I have heard that they don't work if doing a word replacement and then putting the word in the replacement also - like replace google with a link to google (
www.google.com)