Disemvoweling (also spelled disemvowelling) is a technique used by forum moderators to suppress trolling, vandalism, and other rude behavior in online discourse by removing all the vowels from the offending material.
The disemvoweled text can still be read, or rather puzzled out; but it is clearly marked as deprecated, and is no longer susceptible to being automatically read by every passer-by who happens to glance at it.
Finally, the disemvoweling convention can be used by the participants themselves, to preemptively dsmvwl pssgs whch my b smwht ffnsv—though admittedly, self-disemvoweling is most often done for humorous effect.