I’ve started using a little CSS hack for when I want to reblog a fellow Tumblr user’s post and “comment” on it, but do not wish to have my resulting “reblog” post actually appear on my public-facing website.

(You see, I hate the fact that if I’m simply making a comment or joining in on some Tumblr dashboard conversation, then the people who view my public site, some of whom are NOT Tumblr users, are seeing posts that are totally irrelevant and confusing. And since the only current way to “comment” on something in Tumblr is via the “reblog” feature, I am forced to do the following…)

STEPS:
1. Make sure you’re editing your custom HTML/CSS for your theme.

2. Inside the <style> tags, give yourself a class style like the following: 
.commentary {display:none;}

3. Then, on each of the post types in your HTML, include the following in the class property: {TagsAsClasses} This is Tumblr’s way of letting you apply whatever TAGS you have given your post, as classes.

4. Give your “comment/reblog” posts a TAG of, you guessed it, “commentary.”

The result is that the posts with the tag/class of “commentary” don’t get shown to your public guests, but they DO still show on the dashboard, where they belong.

In the end, your HTML for each post should look something like this.