In Section 5.7.5 (page 23) "security concerns" are cited as the reason to reject the following code points: 
U+01C0 LATIN LETTER DENTAL CLICK
U+01C1 LATIN LETTER LATERAL CLICK
U+01C2 LATIN LETTER ALVEOLAR CLICK
It is not clear just what those security concerns might be. 

After all, the U+01C0 is just a vertical line.  And the MSR already includes several code points like that.  For example: 
006C Latin Small Letter L 
04CF Cyrillic Small Letter Palochka 
05D5 Hebrew Letter Vav 
0627 Arabic Letter Alef 
4E28 (CJK Unified Ideograph)  

Similarly, U+01C1 is merely two vertical lines.  In addition to the obvious occurrance of a repeat of the previous code points, MSR contains: 
05F0 Hebrew Ligature Yiddish Double Vav 
5202 (CJK Ideograph Knife) 

And U+01C2 is a vertical line crossed by two shorter lines.  As are MSR entries:  
2C61 Latin Small Letter L With Double Bar 
624C (CJK Ideograph Hand) 

Considering that all of these are sufficiently similar to warrant serious consideration as variants of the rejected code points, it would be useful to explain, in some detail, exactly why the rejected code points present security concerns, while the included ones do not. 

Bill Jouris