[Axel13]

Since the page you refer to, Pascal, says:

Unfortunately, it’s difficult to ascertain from within bbPress exactly what other plugin causes this to happen, so bbp_setup_current_user comes up in the logs.

Perhaps it’s useful to know that I also see this notice, yet only on localhost and that Yoast SEO has something to do with it. The notice disappears when deactivating Yoast SEO. I do not see any notice when activating both plugins on my site.

Here is the error with some more details:

( ! ) Notice: bbp_setup_current_user was called <strong>incorrectly</strong>. The current user is being initialized without using $wp->init(). Please see <a href="https://codex.wordpress.org/Debugging_in_WordPress">Debugging in WordPress</a> for more information. (This message was added in version 2.3.) in C:\wamp\www\wp\wp-includes\functions.php on line 3622
Call Stack
#	Time	Memory	Function	Location
1	0.0026	424608	{main}( )	..\plugins.php:0
2	0.0032	493464	require_once( 'C:\wamp\www\wp\wp-admin\admin.php' )	..\plugins.php:10
3	0.0035	511616	require_once( 'C:\wamp\www\wp\wp-load.php' )	..\admin.php:31
4	0.0037	522552	require_once( 'C:\wamp\www\wp\wp-config.php' )	..\wp-load.php:37
5	0.0042	620608	require_once( 'C:\wamp\www\wp\wp-settings.php' )	..\wp-config.php:89
6	0.1986	28145704	do_action( )	..\wp-settings.php:237
7	0.2427	32127520	call_user_func_array:{C:\wamp\www\wp\wp-includes\plugin.php:503} ( )	..\plugin.php:503
8	0.2428	32127584	wpseo_admin_init( )	..\plugin.php:503
9	0.2432	32196168	WPSEO_Admin_Init->__construct( )	..\wp-seo-main.php:292
10	0.2464	32361392	WPSEO_Admin->__construct( )	..\class-admin-init.php:31
11	0.2493	32460912	WPSEO_GSC->__construct( )	..\class-admin.php:42
12	0.2493	32462088	current_user_can( )	..\class-gsc.php:60
13	0.2493	32462120	wp_get_current_user( )	..\capabilities.php:1441
14	0.2493	32462392	get_currentuserinfo( )	..\pluggable.php:60
15	0.2516	32513872	wp_set_current_user( )	..\pluggable.php:125
16	0.2520	32542032	do_action( )	..\pluggable.php:41
17	0.2525	32547552	call_user_func_array:{C:\wamp\www\wp\wp-includes\plugin.php:503} ( )	..\plugin.php:503
18	0.2525	32547632	bbp_setup_current_user( )	..\plugin.php:503
19	0.2525	32548072	_doing_it_wrong( )	..\sub-actions.php:147
20	0.2527	32549376	trigger_error ( )	..\functions.php:3622

I hope that helps!