This has always bugged me
 

While being the BU in a high school varsity game between to rival schools (and some great baseball being played) the situation was this:

Bottom of the last inning, score tied, bases loaded, outs don't matter (partially because I can't remember how many). Ball is live. Pitcher with ball in his glove step on the mound in the set position. As soon as the pitcher steps on the rubber I focus on him. While the runners were on their bases getting signals from the coach, the pitcher, while still on the rubber, pulls the ball out of his glove and down to his side.

This is balk, correct?

I stood up and started to call it. But a lot of things crossed my mind in those couple of seconds: A balk would have ended this great game. I don't think anyone seen it except me. I don't think he was trying to do anything tricky - I think he just didn't know.

Then I thought to myself, "what if the other coach also seen it and then questioned why I didn't call it?" Would I have pretended not have seen it?

What would you have done? No harm no foul?

Do you let the type of game (Varsity, Rivals, 0-0 game in the 7th, etc.) dictate how you ump? Tighter strike zone, etc.

I think this no-balk call is really the only thing I've ever questioned myself on over the years. Thought I would throw this out there.

Although the words say "the pitching regulations begin when the pitcher intentionally contacts the rubber with the pivot foot", they really mean "the pitching regulations begin after the pitcher has gotten "comfortable" on the rubber."

So, if there was some delay between getting on the rubber and removing the ball, call it. If it was all part of the motion to look in for the sign, then let it go.

When I used to officiate Ice Hockey, there were times that some very minor penalties could be over-looked, depending on the level of play, tone, score and whether or not a team gained an advantage as a result of letting the penalty slide or not. In fact it was covered in the officiating manuals and was part of officiating that sport.

Baseball is a little similar however, there are fewer violations of the rules where a team can easily gain an advantage, if you fail to make the proper call. Don't put yourself in that situation. There are times where preventive umpiring can handle things during a crucial part of the game but for the most part at the Varsity level, "Make the call"

Then again, make sure that you are 100% correct about making a balk call when you have to. Wrong call, advantage offense.

Was it the first time that game a pitcher had done this?

Good point. But it might have been a reliever who just did it. If it was Bob Jenkins gave good advice. When asked, very rarely, why I don't balk this I tell whoever that I had momentary adjustment. Which is adressed in OBR but not in FED.
If you are a new or unread umpire you will balk this. If you are a studied umpire you will understand not to balk this.
In either case, by this time, everybody should know they can or can't do this.

References are MLBUM and JIm Evans Balk video.

Yes it was the first and only time he did this Reffing Rev. In my opinion he wasn't trying to be deceiving - he just decided he wanted the ball in his hand and not his mitt prior to the pitch - but forgot to disengage the mound. Even my partner didn't catch it.

A balk is committed when it puts the runners at a disadvantage on a possible advancement of bases.

I try and keep that in mind at all times and in my years of doing this, I haven't had any issues.

Don't be "overly officious."