Use `%%` to enclose comments, which will be parsed as Markdown, but will not show up in the preview.

```md
Here is some inline comments: %%You can't see this text%% (Can't see it)

Here is a block comment:
%%
It can span
multiple lines
%%
```

Here is some inline comments: %%You can't see this text%% (can't see it in preview)

Here is a block comment: (can't see it in preview either)
%%
It can span
multiple lines
%%