Here's my test data, taken from the attached plugin.
Powerlord is my fast desktop
rbemrose is my slow laptop
rbemrose was intentionally connected first to test if client indexes would be reordered during the first map change. And so I could kick it before the second map change.
rbemrose was kicked during ctf_doublecross.
Code:
L 06/18/2013 - 15:53:44: [testclientid_index.smx] Plugin Loaded
L 06/18/2013 - 15:53:48: [testclientid_index.smx] Map change to pl_upward
L 06/18/2013 - 15:53:48: [testclientid_index.smx] Client connected: Replay<2><STEAM_ID_PENDING><>, client: 1
L 06/18/2013 - 16:05:07: [testclientid_index.smx] Client connected: rbemrose<3><STEAM_ID_PENDING><>, client: 2
L 06/18/2013 - 16:06:41: [testclientid_index.smx] Client connected: Powerlord<4><STEAM_ID_PENDING><>, client: 3
L 06/18/2013 - 16:08:48: [testclientid_index.smx] Client disconnected: Replay<2><STEAM_ID_PENDING><>, client: 1
L 06/18/2013 - 16:08:48: [testclientid_index.smx] Client disconnected: rbemrose<3><STEAM_0:1:42523234><>, client: 2
L 06/18/2013 - 16:08:48: [testclientid_index.smx] Client disconnected: Powerlord<4><STEAM_0:0:1081621><>, client: 3
L 06/18/2013 - 16:08:52: [testclientid_index.smx] Map change to ctf_doublecross
L 06/18/2013 - 16:08:52: [testclientid_index.smx] Client connected: Replay<2><STEAM_ID_PENDING><>, client: 1
L 06/18/2013 - 16:08:53: [testclientid_index.smx] Client connected: Powerlord<4><STEAM_ID_PENDING><>, client: 3
L 06/18/2013 - 16:08:53: [testclientid_index.smx] Client connected: rbemrose<3><STEAM_ID_PENDING><>, client: 2
L 06/18/2013 - 16:10:11: [testclientid_index.smx] Client disconnected: rbemrose<3><STEAM_0:1:42523234><>, client: 2
L 06/18/2013 - 16:10:20: [testclientid_index.smx] Client disconnected: Replay<2><STEAM_ID_PENDING><>, client: 1
L 06/18/2013 - 16:10:20: [testclientid_index.smx] Client disconnected: Powerlord<4><STEAM_0:0:1081621><>, client: 3
L 06/18/2013 - 16:10:24: [testclientid_index.smx] Map change to ctf_2fort
L 06/18/2013 - 16:10:24: [testclientid_index.smx] Client connected: Replay<2><STEAM_ID_PENDING><>, client: 1
L 06/18/2013 - 16:10:24: [testclientid_index.smx] Client connected: Powerlord<4><STEAM_ID_PENDING><>, client: 3
L 06/18/2013 - 16:11:53: [testclientid_index.smx] Client disconnected: Powerlord<4><STEAM_0:0:1081621><>, client: 3
As you can see, after the last map (ctf_2fort) started, the only connected client indexes were Replay at index 1 and Powerlord at 3.
So, to reiterate, client indexes are
kept across map changes, as are userids... and "DAT WIKI" really needs to be updated because it's blatantly wrong. In retrospect, I probably should have logged the kick in here as a kick instead of just a disconnect (whoops).