Spam in RSS feed
For those who have an RSS mod installed (e.g. RSS Syndication Mod by Lucas) I recommended to change the spam word filter's setting "How should posts that contain spam words be dealt with?" to "Error message". Default of this setting is is "Flag and hide posts" which works quite well, but the flagged posts are still written into the RSS feed.
= Blocked text still logged
After changing the setting to "Error message" the blocked texts are still written to the "Log" of the spam word filter. Administrators still can see what's going on and even see if there are false positives (but you can no longer accept the false positives, this was possible when flagging posts).
= Spam word in error messages
The error messages shown when a text is blocked are also configurable, by default the spam word recognized is listed in the message text. If you want to make your spammers (and users) life harder, you can change the message text and remove the listing of the spam word.
= No increase in spam after switching
I've switched the setting two days ago. My concern when changing the setting was that spammers could immediately see that their post wasn't successful and repost a modified version of the spam text. But number of logged spams hasn't increased noticably.
All in all only advantages. For those using a RSS mod switching the spam word filter to "Error message" should be interesting.