If I do this right, all the Markdown in this post ought to show up in blue boxes.
I'll be clicking the "Preview" button to check before I actually post, but there's always a chance I'll miss something anyway....
Typing a word or string of words with Markdown on either side like _this_ or *even like this* will give you italics. (Make sure there's no space between the Markdown and the words.)
Typing **something like this** will get you bold text.
Putting > in front of a new paragraph will make that paragraph
>> will give you
And so on.
Putting >! in front of a new paragraph makes that paragraph a spoiler.
You get nested spoilers by typing >!>! in front of your new paragraph.
I'd demonstrate that, but apparently a post full of backticks makes spoilers turn into boxes the same color as the text they hide instead of click-to-expand spoilers! I wasn't expecting that.
Nobody expects the Spanish—oh, never mind.
<font size="1">around words</font> will make them very small. Increase the number to increase the size!
<font style="color:red">around a word or sentence</font> will turn the words red. Change the color to, well, change the color.
<font size="5"><font style="color:blue">You can **combine** these, of course.</font></font>
You can combine these, of course.
> *<font style="color:purple">Any</font>* way _<font size="4">you</font>_ want.
Found a picture online and want to share without saving it to your device? Copy the image's URL (a right click or long press will give you the option to open the image in its own tab: you can copy its URL from there), and put in it in Markdown like this:

That will give you this:

To add an image description (for screen readers, or to show up if the image ever gets deleted), put the description between quotation marks after the link, like so:

Remember to put a space between the end of the link and the first quotation mark.
In-text links are done by putting the text you want to be clickable [inside brackets, and sticking the link itself in parentheses directly after](https://www.dogalize.com/wp-content/uploads/2017/04/pallas-cat.jpg).
Like this: inside brackets, and the link itself in parentheses directly after.
That's all I can think of at the moment. Please, feel free to add any tips and tricks you've discovered!