Posted something yesterday , did you see that?

You mean this one ?

You mean this one ?

yes

It is there, so at least the spam engine didn't get it... 

It appears that sometimes new content is slow to get indexed by the search engine, which means that it won't initially show up in the results of search-based activity lists. When it does finally get indexed, it can be 12-24hour old content and is quickly buried over by the newer content and easy to miss. 

I believe the reason is that I answered on an old (march 2021) post of myself. You could test it for yourself by looking up one of your older blogs and comment on it. I think that there is no channel at this moment that generates notifications for those.

Several posts submitted after this one, including some of mine, got on the notification channel.

I think you may be looking at two different things here ?

For comment notifications, I think everyone would need comment notifications to be turned on for the individual blog post... 

...in addition to the general notification settings in your profile. I think this flag automatically gets set if you add a comment to a blog post.

The feeds however are often search engine based, so the update likely needs to be indexed in the search engine before it shows up. Presumably these results are also cached on the likes of the home page to speed things up.

Hi Jan,

You're right, this is a known issue, that the main page recent content only sorts by date of creation of the original article (blog or discussion or document), and not by date of the last comment. As a result, it is not possible to discover comments on old posts (or edits to old articles I think) from the main page.

There was some brainstorming of ideas in a separate post (the one where we tried to redesign what that first page behaviour could look like), for hopefully consideration in a later release, but I don't know how far that got.

A workaround for those interesting in multiple engineering fields (like us I guess) could have been notifications, but for some articles, people might not have subscribed to notifications either (and that's another issue, that there doesn't seem to be a simple way to get notified of 'everything' (comment-wise, and not say status-wise which is not essential), since then it could be sorted via e-mail rules and folders). I'm sure I'm not registered for all notifications, since I didn't see an e-mail on the Arduino item you mention.

the gist if: if I post something and no one (I believe that in this case no one gets a notification for real) gets a notification and it does not show on the home screen at any time - then what's the point of posting it?

I'm not posting for the eventuality that someone at some time will search for DIN, Arduino and MOLEX, then switch notification on and receive subsequent updates. 
On a community, the goal is communication. And that only happens if at least one person sees your post.
 

If I post something and no one (I believe that in this case no one gets a notification for real) gets a notification and it does not show on the home screen at any time - then what's the point of posting it

Totally agree. It makes it almost worthless to write a comment on an old post, unless it's specifically only addressed to someone you are replying to, and isn't information of interest to others, because others most likely will not see it, due to the current limitations. Only new articles (blogs or discussions, not comments or updates) are worth creating in such a situation.

It really needs addressing, because it's very crippling, but I believe (hope) someone is perhaps working on it, it was raised early on, a couple of months ago, when we were asked about ideas on how to address this issue.

Not totally sure but it looks like Forums may work better than Blogs for visibility ?

If you are subscribed to a Group and someone creates or responds to a Forum post in that Group, then by default it appears that you will get a Notification ( unless you opt-out with the Mute flag ). You have to opt-in to join the group, but then opt-out not to get a notification, whereas with blogs you appear to have to opt-in to get the notification. 

Unfortunately if the old post being commented on has been posted as a Blog, then this doesn't really help for older content.

Since the migration, I tend to use the search engine to see site activity, so the comment reply to your older blog post showed up in my 'feed' (as per the earlier screenshot) without having specifically to search for "DIN, Arduino and MOLEX". However not everyone will use this method. You should however get the same result if you used the 'View more results' option on the home page Blog feed. As has been pointed out, it doesn't get the top billing on the home page as that appears to be based upon date of original post rather the the date of the last comment. 

“Since the migration, I tend to use the search engine to see site activity”
this here sums up what’s wrong; forum software has, for decades now, listed new/updated content on latest date order.  The fact that this software doesn’t is bananas.  No one should have to use the search or site map page as a matter of course in finding new content; that’s an anti-ux pattern right there and against the grain of user knowledge for site usage and navigation.