As suggested by wakest on issue #226:
I just noticed that you can change your username on writefreely and thought that was quite strange since its the first software I have noticed in the fediverse that has this ability. If I am following a writefreely account from mastodon and I change my username, I am not automatically following the new username, and I am still following the old one. so if I change my username 10 times I can separately follow 10 different accounts. I am unsure of all the repercussions of this but I can think of many. I think at the very least there should be a warning that changing the username is not recommended due to some incompatibilities or issues with federation between other parts of the fediverse.
was playing with the new instance https://scream.today (running writefreely v0.11.2)