According to specification (1.04, part 5, 6.3.1 - ServerType) the serverUri shall be case sensitive.

The serverURI shall match the applicationUri (in ApplicationDescription) and shall match the application URI in the certificate, all of them should be compared case-sensitive???

This contradicts the RFC 2141, where is stated:
URN Syntax
...

2. Syntax
   ...
   <URN> ::= "urn:" <NID> ":" <NSS>
   where <NID> is the Namespace Identifier,
   and <NSS> is the Namespace Specific String.
   The leading "urn:" sequence is case-insensitive.
   ...

Somewhere later it is stated:
Further, the Namespace Identifier is case insensitive, so that "ISBN" and "isbn" refer to the same namespace.
and:

5. Lexical Equivalence in URNs
   ...
   Two URNs are lexically equivalent if they are octet-by-octet equal after the following preprocessing:
   1. normalize the case of the leading "urn:" token
   2. normalize the case of the NID
   3. normalizing the case of any %-escaping
      Note that %-escaping MUST NOT be removed.
      Some namespaces may define additional lexical equivalences, such as case-insensitivity of the NSS (or parts thereof).
      Additional lexical equivalences MUST be documented as part of namespace registration,
      MUST always have the effect of eliminating some of the false negatives obtained by the procedure above,
      and MUST NEVER say that two URNs are not equivalent if the procedure above says they are equivalent.

In the OPC UA specifications I did not find any further hint, how URIs shall be compared, however URI mismatches must not be suppressed.

In part 4 (6.1.3) it is stated
Application and Software Certificates contain an application
or product URI that shall match the URI specified in the
ApplicationDescription provided with the Certificate.
This check is skipped for CA Certificates.
This error may not be suppressed.
The gatewayServerUri is used to validate an
Application Certificate when connecting to a Gateway Server (see 7.1).