You seem to be using a central login system (https://identity.kde.org/) that requires going to a separate website to create an account which presumably is non-standard enough to throw off most bots.
invent.kde.org uses the nonfree google Recaptcha, that prevents it mostly. Not very nice for KDE to make people run nonfree software blob in their browser that gives up their freedom, gives up their privacy to google and trains Google's proprietary machine learning models.
