Add an option to show a summary of posts on the home page

This is handled by your theme’s template files – not WordPress core.

I’m asking for this feature to exist. Currently it does not.

Yes it does. See the_excerpt().

Are you offering to code this feature for me on every site I own and then recode it on every update to wordpress?!? ?? That’s so nice of you! ??

Please, I would really like to have this feature as I described.

It already exists and has done for years!

It’s not an option, monkeypunch3, it’s a choice. You can go edit your theme to use the_excerpt() instead of the_content(), or not. If a theme wants to give you that option in it’s own settings, it actually can (many do), but that’s their decision ?? And when you disagree, you can make a child theme.

I understand you are directing me to edit the php files.

I’m saying I don’t want to edit any files. I would like to have an option in the user interface.

In the Twenty Eleven theme there is an option, “For each article in a feed, show ” and then two radio buttons, “Full text” and “Summary”. I can select the option.

I’m saying that having that for posts on the home page would improve my experience with WordPress (obviously).

I can select the option.

That’s for your RSS feeds – not your content display on your site. The latter is governed entirely by your theme – not WordPress core.

I’m saying I don’t want to edit any files. I would like to have an option in the user interface.

If the theme doesn’t offer that (and please understand, it’s something that realistically only your theme can offer, since not all themes would have this available), then you must edit the files by making a child theme.

Or someone clever could probably make a plugin that did it.