I always tweak when I repost too.

If I have trouble understanding or paying attention to what I wrote originally, I'm forced to admit that the essay was never good per se and I should fix it before I redistribute it.

But sometimes it's just that what was good for one platform or audience isn't ideal for another.

Other times, the issue is that everyone's focus has changed. An old "urgent action alert" is now "ancient history you might like to know," so yesterday's standalone news story must be reduced to one paragraph of context woven into today's news story. Alternatively, I might make it a personal statement of "here's how I approach this topic because of other things I've paid attention to and written about," etc.