So instead of writing "Guvf vf n grfg", one might do "Guvf vf n grfg", or maybe just "Spoiler".

The advantage of the first method is that it gives you some idea of how long the spoilered text is before you look at it, and maybe recognize the text enough so you don't have to look it up again the next time you want to read the same post. The advantage of the second method is that it conceals everything about the spoiler, and doesn't even reveal any information once you look at the URL.