Edits have been rate-limited a few weeks ago in order to fight vandalism like deleting complete cities or removing names in a certain language. Fighting this vandalism required lots of volunteer resources – both for blocking the accounts and reverting the changes. In addition, blocks were circumvented by new accounts. Therefore, you have to wait a few hours until you can change more features. The good news: The older your account becomes, the higher your limit will be.
There is no official blog post about this but you can find some information by the developers of the OSM website on GitHub and a forum thread where people from HOT complain about rate-limiting limiting their uploads.
EDIT: See also this wiki page.