Note that the profiles of "Former users" are not available and we cannot see their posts/comments history or which particular user wrote the contributions attributed to "Former users". It happens that sometimes a user just wants to take a break.
Please note that the users that have been blocked ("banned") still have their account and comment history. They are not "Former users" as discussed in this topic.
Some may just keep their account and return later. Others may delete their account and return registering with another user name, possibly to comply with Community rule #7. (If I understood your question correctly.)