Strange that you say that, seeing as the playing field in bomberman is completely flat.

Indeed, this is in fact quite the valid comparison. Problem is suiciding in FPS's isn't an invalid tactic either. Even with the point loss it doesn't make it an invalid tactic, less useful yes, but invalid no. Actually on a side note, In a majority of the FPS's I've played (and I can't say anything about blast, never played it). The points are deducted for causing yourself to die. Then points are again added for the kill you made. This is why in many games if your death is certain tossing a grenade out is common play, and will not lose you points. This is even implemented in game by COD4s Martyrdom perk. (which itself is often called noobish and unskillful, but its very much still part of the game). It does beg the question though in blast are points deducted for suicide killing or for suicide. If the point deduction is for killing yourself it in no way proves that it was implemented to prevent suicide kills, just to prevent stupid play and possibly slightly weaken suicide kills. Even if it IS implemented only on suicide kills, you're going to have a hard time telling me that bomberman blast isn't a different game then super bomberman 3, and even then you're going to have a hard time telling me that a point punishment is enough to make me dismiss the strategy as a valid one in certain situations, playing a game is all about weighing your options and taking the best one. And suicide in some cases MAY be your best option. (let me give you a hypothetical situation, you are playing a timed game and and your team is winning. The timer is almost up but you are in a position where you can assure your team wins by suicide. Do you let the timer run out and start a full new round negating your man advantage. If your goals are to you know, win the game, you should, because that will give you the round win AND net you gained points for the round which would otherwise count for nothing.)

Unspoken rules are in no way rules. And I've seen people kick players who were better for them for the reason that they are better then them. Does that make being good at the game an unspoken rule?

You'll never see me enforce unspoken rules on myself. If they're spoken as tournament rules then I will follow them because I don't want to be disqualified. If you say the rules before I enter the game I will follow them or leave (I am not a griefer, as much as you may enjoy calling me one for not following unofficial rules). But I will not enforce phony rules on myself.

There is an article about this kindof thinking that I rarely link to due to the fact that the point can be made in a less obnoxious manner. I present for your reading pleasure, an article by a tournament level fighting game player (as in gets into the top ten of street fighter series tournaments). It (somewhat rudely) states something pretty close to my opinion.
http://www.sirlin.net/Features/feature_PlayToWinPart1.htm

--edit--
After doing a bit of searching I found this.
http://www.gamespot.com/wii/action/bombermanblast/show_msgs.php?topic_id=m-1-45907448&pid=945463

It claims the penalty for suicide is the same as the penalty for dieing by someone elses bomb, someone want to confirm or deny? That's not a punishment at all. If this is accurate you'd get a score of 0 if you suicide bombed someone wouldn't you? 20 points lost for suicide and 20 points gained for bombing others. I have not bomberman blast, so impossible for me to say for sure.