How can I display a comment textbox after each post?

You can make a child theme and change the way comments are handled there.
Or you can switch themes to one that handles comments the way you prefer.
There are also a lot of plugins that affect how comments are handled.

Thanks. I definitely need to get more familiar with css. I’ve tried with a couple of plugins, but apart from their individual bells and whistles, they don’t seem to affect this display behaviour on already existing posts.

After tinkering a little with css, I realized that learning css is far beyond my scope. I’ve also tried a number of discussions plugins but none of them seems to offer any additional option as to how to display the comments box.

I would be very thankful if anyone could tell me how to do such a simple thing: displaying a comment box at the end of my posts or any icon suggesting the possibility of commenting, at the bottom of the post, rather than with the tiny envelope icon below the title, where it is unlikely that anyone would go after reading the post, and which is standard for the Twenty Twenty Theme

• This reply was modified 4 years, 10 months ago by pieemme.
• This reply was modified 4 years, 10 months ago by pieemme.

This doesn’t have anything to do with CSS, really, unless you have added some that hides the comments section.
I was just testing Twenty Twenty with all the variations of comments, no comments, comments disabled, trackbacks, password protected, and they all display correctly at the bottom of the page.
If you want to change how they display, copy the comments.php from the parent to the child and change it in the child.

Edit: if you don’t have your Discussion settings to allow comments, new posts won’t show the comment box. But the Discussion settings only apply to posts that are created after you change the setting. All existing posts have their own setting for whether comments are allowed or not (set to whatever the Discussion setting was when the post was created).

• This reply was modified 4 years, 10 months ago by Joy.

Thanks for your suggestions. However I simply have contrary evidence on my site: https://www.scienzaespirito.com.

You can see how the comments are almost hidden – there aren’t any right now ??

Here is a Screenshot

The comments are shown only when clicking on the callout icon, which has an ancor link opening the comment box.

I eventually opted for the Twenty Seventeen Theme, which offers a friendlier display. I am leaving Twenty Twenty on for a few hours longer, hoping you have a chance to look at it.
BTW, I haven’t made any customization other than changing some images.

• This reply was modified 4 years, 10 months ago by pieemme.
• This reply was modified 4 years, 10 months ago by pieemme.

Your screenshot looks normal, and so does your site. The default for WordPress comments is that they only show on the singular page. Your site home page is showing the Latest Posts, so when you click to one of the post pages, you see the comment box at the bottom as expected.
It is complicated to get WordPress to behave differently, and show comments on each post on an archive page (list of posts).

Thank you, everything is clear. Now I can roll back to Twenty Seventeen, which handles comments more to my taste ??

Further to my earlier posts and for better clarification: I realise now that the confusing appearance of my posts, (apparently not commentable) was determined to their being displayed in full length, rather than in abridged form (read more). When there is no need to click to view the entire post, because it appears in its entirety, the comment block stays hidden.

The next step is finding a way to add a read more block to my posts, which doesn’t seem to be available in the current block editor.

The Twenty Twenty theme has the option of showing full posts or excerpts. I don’t think the Twenty Seventeen theme has this option.
To understand the Read More block (which is indeed in the block editor) or tag (classic editor), you should understand that it only does something when the full content is being shown on a list page. When it is, the content before the Read More is shown, and then a Read More link which links to that location in the single post page.
When a theme is showing excerpts, Read More is ignored. The excerpt is first sought from the manual entry of excerpt, and if that’s empty then the excerpt is generated from the first 55(default but can be changed) words with HTML tags stripped. The manual excerpt can contain HTML tags.

So if you have decided which way to show your content, you will probably want to stick with that if you switch themes, since you will already have put Read More or manual excerpts — or neither.

Thanks again. Read More is working on Twenty Seventeen too. Only it took me some time to find the option because I was expecting to find it in the Block formatting menus, while it is in the Layout options.