You Want to Be Effective and Efficient
Having the administrators ban by user name is E&E only if the object (1) is too lazy to adopt another user name and (2) register under that name. IP bans may be somewhat more effective but remember (1) a single IP address may service many users and you may block legitimate uses if they happen to have the same ISP (2) it is often possible to obtain a new IP address more quickly than a new user name (3) spoofing IP addresses isn't that difficult (4) an unsecured wireless point may provide access to an irritant even if the owner doesn't know OCDO exists. The ignore option is easy, quick and effective - at least temporarily. A scapel not a meat cleaver.
Having the administrators ban by user name is E&E only if the object (1) is too lazy to adopt another user name and (2) register under that name. IP bans may be somewhat more effective but remember (1) a single IP address may service many users and you may block legitimate uses if they happen to have the same ISP (2) it is often possible to obtain a new IP address more quickly than a new user name (3) spoofing IP addresses isn't that difficult (4) an unsecured wireless point may provide access to an irritant even if the owner doesn't know OCDO exists. The ignore option is easy, quick and effective - at least temporarily. A scapel not a meat cleaver.