Separate from body in feeds

I’m wondering if there is some code that can be added to style css or in a post itself.

For example I type a post like this:

<h3>June 14th - Spiderweb</h3>
A spiderweb is something that had been on my to-shoot list for the 365 project for a while. Today I finally had the chance to fulfill this task.
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But when I share this to Facebook it come out like this:
June 14th – Spiderweb A spiderweb is something that had been on my to-shoot list for the 365 project for a while. Today I finally had the chance to fulfill this task.

This is also the case in Feedley and I recon with every application that picks up the /feed.

Is there a way that I can distinguish the head from the body? I tried adding a <b>tag but wp removes that when saving the posts.