From DYOS Wiki
Not to be confused with <Expletive deleted>

[DATA EXPUNGED] is a running gag used by the Styles brothers whenever they say something, but don't actually reveal what they were saying to keep it a secret from the readers. Usually when the gag is used, Mikuru Asahina is somewhere around to force the censorship.

Sometimes the data that is expunged is just something you don't want to know...

There is also an [EXPLETIVE REDACTED] which is much like <Expletive deleted>.

Behind the scenes

It is commonly used by the SCP Foundation, a web original based on finding creepy or dangerous objects and containing them. Many of the objects there are so dangerous, the effects or research are hidden by censorship, such as black censor boxes and [DATA EXPUNGED] tags, leaving it to the imagination on what might be the effect and how bad it really is.

The reason why Mikuru uses it a lot, is because it makes sense with her character, who hides information by saying "Classified information". Change the words to [DATA EXPUNGED] and you have an SCP Foundation Agent...