The poster of that translation explictly stated that it may have errors in it especially in the parts where the Master of Masters speaks so you should probably take all these statements with a grain of salt and wait for an official translation before jumping to conclusions.
Furthermore, "dangerous" can mean many things, it doesn't have to mean "evil" or even "antagonistic".
There is the speaking that "curiosity killed the cat" and Ephemer, while friendly, cute and really supportive, is also shown to be inquisitive and very curious so he has to stick his little nose everywhere where he thinks he might get more knowledge on how the world works.
He also pestered Ava more than once about the book and tried to get information about it.
This can also become "dangerous", to both Ephemer himself and those associated with him depending on the situation.
Skuld is shown to be assertive and not afraid to stand her ground and defend her beliefs and convinctions, as shown when she breaks up the fight between the two Keykids in one of the last updates in browser chi together with Player and chews them out on how they're using their Keyblades wrong, dismissing the question from which union she is as irrelevant to the matter at hand.
Such an attitude and conviction can too be "dangerous" depending on the situation.