I have noticed people use change logs on their posts but it isn’t necessary as the function is already part of Discourse.
Step 1 - First click on the pencil on the top right corner of a post (next to the date).
Step 2
You can view in 3 different ways.
a) HTML - This shows each iteration of changes.
b) HTML Compare side by side - This view can show the timeline of changes.
c) Raw - Viewing as Raw makes it easier to copy into a text edit file
Pretty simple and neat.