this is an example.
[glow=black,2,300]this is an example.[/glow]
The only downside is that you cannot view the text on mobile devices.
When you're creating a very long post that's split into sections, using spoilers it'll look better and won't bother users to scroll way too much around.
For example, consider my post here: https://bitcointalksearch.org/topic/list-of-stuff-you-can-use-bitcoin-for-3097705 as the list grows and gets separated into categories, it'll be awesome if I could put the category name only, with spoiler tags under it, so you only expand the category you want to read instead of having to scroll over all categories.