Honestly I am incredibly fed up seeing comments on peoples costumes/pictures from people who are completely stuck up and find it upon themselves to call out and belittle people who are not "true" steampunkers.
In the end it is a fantasy based style. If you mix a little steampunk in with dieselpunk so what? I think it would be much more constructive to support each other and step down off of the pedestal that you have put yourself on.
And if you step back and think about it I'm sure when you were first getting into steampunk, dieselpunk, atompunk or one of the other genres you did not know everything so instead of calling someone out and making them feel bad why don't you try and help them out instead.