Behavior of case sensitivity of RAISERROR when run remotely
This issue may actually be related to a very old bug with SQL Server, but not directly caused by SQL Server itself.

I found this MSDN thread which describes the exact same behavior


  Please note the strangeness of this: RAISERROR won't compile (connection time out), even if it is in a comment!


This was the accepted answer


  It turns out that the network that our SQL Server is on has an intrusion prevention system.  In that system there is a filter with the following description:
  
  This filter detects access to the raiserror procedure on port 1433. The raiserror procedure in a Microsoft SQL Server contains a buffer overflow vulnerability, which can be remotely exploited to execute arbitrary computer code on the affected system, thus allowing an attacker to gain complete control of the server. The procedures known to be vulnerable are: xp_sprintf, raiseerror() and formatmessage(). If the overruns are exploited, the code runs in the context of a local administrator account.


There is an old MS Security Bulletin for this bug and a more recent TechNet thread describing the same issue.

It's possible there is something on our network that I am not aware of that is filtering out anything with the text raiserror in it (but doing a poor job of it since the check is case sensitive). Not that it matters since the bug was fixed.

Since this isn't recognized behavior of SQL Server then it could likely be a network configuration issue.