Developing a module, I've found, that ModuleAuditControl misses it's content in a postback. Setting EnableViewState="true" in ascx has no effect. 

Searching further, I've found that ViewState is disabled in ModuleAuditControl labels (moduleauditcontrol.ascx file):

<%@ Control Language="C#" AutoEventWireup="false" Inherits="DotNetNuke.UI.UserControls.ModuleAuditControl" %>
<div>
<p><asp:label id="lblCreatedBy" runat="server" CssClass=SubHead enableviewstate="False" /></p>
<p><asp:label id="lblUpdatedBy" runat="server" CssClass=SubHead enableviewstate="False" /></p>
</div>

I don't see any meaning in disabling ViewState on this level - so what logic was behind this?..

Note: This wrong behaviour of ModuleAuditControl affects many 3-rd party modules, by example popular Documents module.