bryan here does not support CBC, nor did it have FiSH enabled. lolwut is using FiSH10's CBC mode.
The CBC is still vuln to replay attack as it does not take the previous data seen into account for its IV, which it really can't anyway as messages are not guaranteed to come through in the same order to all clients (even in a private message scenario).
Seen from IRSSI:
20:04:31 < lolwut> +OK */+oAlEKOmjasKT9tlEv7Cw==
20:04:33 < lolwut> +OK *BsYMtHPWPmP+0z3RMLEgOA==
20:04:34 < lolwut> +OK *zj7vwK9O7TLW5h26hPjAJg==
20:04:35 < lolwut> +OK *332AXN/zGv56bPf3X9ZrBw==
20:04:36 < lolwut> +OK *+QUyxu9bx+yZi/2ZuEZTuQ==
20:04:36 < lolwut> +OK *nEDGRtiARhp1WGZT7A7L8Q==
20:04:38 < lolwut> +OK *NapbwQ8FvgXgjeL2DmxsYw==
20:04:39 < lolwut> +OK *4fWnS34hcYyxSpt/XEsoyA==
20:04:44 <@bryan> +OK *4fWnS34hcYyxSpt/XEsoyA==
20:04:45 <@bryan> +OK *4fWnS34hcYyxSpt/XEsoyA==
20:04:46 <@bryan> +OK *4fWnS34hcYyxSpt/XEsoyA==
20:04:46 <@bryan> +OK *4fWnS34hcYyxSpt/XEsoyA==
20:04:48 <@bryan> +OK *+QUyxu9bx+yZi/2ZuEZTuQ==
20:04:49 <@bryan> +OK *+QUyxu9bx+yZi/2ZuEZTuQ==
20:04:51 <@bryan> +OK *BsYMtHPWPmP+0z3RMLEgOA==
20:04:54 <@bryan> +OK *zj7vwK9O7TLW5h26hPjAJg==
20:04:58 <@bryan> +OK *332AXN/zGv56bPf3X9ZrBw==
20:05:54 <@bryan> +OK */+oAlEKOmjasKT9tlEv7Cw==
20:06:00 <@bryan> +OK *BsYMtHPWPmP+0z3RMLEgOA==
Seen from mIRC:
*** FiSH: Key for #wraith-devel set to *censored* (CBC Mode)
<lolwut> woah
<lolwut> sup
<lolwut> sup
<lolwut> sup
<lolwut> sup
<lolwut> sup
<lolwut> sup
<lolwut> sup
<@bryan> sup
<@bryan> sup
<@bryan> sup
<@bryan> sup
<@bryan> sup
<@bryan> sup
<@bryan> sup
<@bryan> sup
<@bryan> sup
<@bryan> woah
<@bryan> sup