Nicer, but (not important) a bit of spacing below title would rad better and (slightly related but more important): text string could be improved to be more helpful:

The message is already in the "administrator section" and "messages menu item" not very helpful, as there is no "messages" menu visible: Proposing to remove "administration section" as we're already there, and add the main menu item name to the text.

The PR basically just uses a straight Bootstrap styled <div class="alert alert-info"> so any change for the spacing, unless we add more specifically targeted CSS, is going to affect all alerts.

The menu item is actually called Post-installation Messages, so it's describing the menu structure already. The admin part agreeably is redundant. I don't mind updating the text, but I wanted to make sure we had something that was at least visually usable for the beta package at this point.

The text string is totally unrelated issue to the styling unless you are saying there is a reason to change the key. Let's maintain focus, and not have scope creep in issues (which should always be kept as granular as is practical).

I know it's not a beta 1 release blocker ;-), However, this is the first item that people see when they login, so styling and content are very important imho, and your styling improvements are really welcome ;-)

This is not about content itself, but about styling it:

• Looks like <h4> in this alert context is missing padding below it. Btw, semantically, to be coherent with modules, it should be <h2> imho, (possibly with same CSS class as modules ?) which would probably solve the issue.
• More important (as affects translations and html/css styling): at first glance I did not catch that "Components" was part of the menu item instructions. maybe something like

Components menu, Post-installation messages sub-menu item

or

Components / Post-installation messages menu item

or even:

"Components" / "Post-installation messages" menu item

or (would need a try):

<span class="label label-info">Components</span> / <span class="label label-info">Post-Installation messages</span> menu item

Could make it clearer that those are the menu + sub-menu items, imho.