Just successfully installed with a similar configuration.
There wasn't any issue.

What's in php.ini in open_basedir param?

By default:

;open_basedir =

Should I've asked the question somewhere else as a non Dev? I'm not too familiar with how things work on Elgg forums. :/

Basically all I had were 2 issues regarding Elgg. The upload plugin that let almost any kind of file upload. And fixed that last time I tried to use Elgg, editing one plugin file. And this one, where I'm not shure where to edit besides thewire.php. Or exactly what. And I'd just be happy to find a "fix" and start using Elgg.

I meant if you want the non-standard features then you should learn to develop as well but not be a "help vampire" (on your reply).

Regarding your question use this snippet:

$reply = $entity->reply;

if ($reply) {
      $class = 'reply_class';
} else  {
     $class = 'no_reply_class';

} 

$params = [
     'title' => false,
     'tags' => false,
     'access' => false,
     'icon_entity' => $entity->getOwnerEntity(),
     'class' => 'thewire-post ' . $class,
];

mod\your_plugin\views\default\object\thewire.php

Thank you. I'll use your advice. 

Not shure if or what's gonna change for the Wire-Activity River in Elgg 4 but this should make it there not being some heavy coding but very usefull, though.

Digging into Elgg a little more it looks to me like a very good platform. Almost wordpress like user friendly. But, I guess, it's aimed more at developer user that can fix some of that platform features to output a decent comunnity site with Elgg. 

An user registered on my future site would be pretty confused not seing his reply under the wire post it replied to but after it with no apparent connection to the parent post. Also this feature on a site with 100 users from wich at least 30 post and reply in a hour, would get even more annoing.

Also confusing is the existence of both the wire page and all site activity page that is a river without the posting form.

But, I guess, it's aimed more at developer user

But you ask as developer so  ¯\_(ツ)_/¯

Look at some existing plugins by hypeJunction: 1, 2, 3

Search. Learn. Try.

I'm sure that after learning Elgg you will be able to create similar sites 1, 2 with customized TheWire in the future.

I didn't said I'm a developer, nor didn't know this is a developer area of the forum.

For me Elgg looks like a good framework for it's purpose but with some confusing bits here and there. Started with the 3.0 and they aren't any plugins for it yet, free or paid that could eventually help me solve my issue.

Doing it myself... I just managed to fix the feature that let users upload viruses on the site. Stopping the extra page loads on every wire comment, and putting the comments under the parent post, it's a little more complicated than that. I'll look at the documentation and hypejunction plugin to figure out something.