I still hold that precisely because of that mIRC should not cause further confusion by hotlinking on some valid channel chars but not on others. Do it consistently or not at all.
Of course there's a potential for confusion in abovementioned server setup. I agree that it's suboptimal. But the issue is of server-side origin and hence should be addressed by the server, not by the client. Also, the chance of the server being configured like that deliberately is considerable, in that case mIRC should not patronize its users.