Information is important to creating welcoming worship, but perfection actually is NOT. What you are striving for instead of perfection is TRANSPARENCY. Make it clear what is going on. Even if your culture is one that wants a feeling of mystery, the mystery should be God, not what is going to happen after the scripture reading. The mystery of the Eucharist is how it provides forgiveness, not knowing when to talk and when to be quiet.
I was at unwelcoming worship the other day, following along with three books and a pamphlet. Although the worship was not in my tradition, I'm pretty good at getting the signals (and I read ahead instead of listening to the sermon so I would know what to do at communion). So when we arrived at the altar for communion (and we did arrive, there was a procession to the altar) I was pleased that I had successfully kept both the worship book and the hymnbook in my hands, so I could sing the sanctus with everyone else.
But after the sanctus, the words of the Eucharistic prayer didn't match the page number that had been published in the bulletin! I looked around to see who else was confused--and there were three of us looking lost--all members of other denominations. In fact, we were the only three holding prayerbooks. The others had the responses memorized. As the community continued with some other prayer I did weight lifting exercises with my two books.
Is it ok to have a mistake in the bulletin? Of course it is! But it isn't ok (or more accurately, it isn't WELCOMING) to continue with worship without explaining what happened. Someone needs to notice that the newcomers (or the priest!) are all on the wrong page. Someone needs to share.
This shouldn't be a big deal. I was once at a worship once were the priest in the middle of the Eucharistic prayer figured out that one person had lost their page. Without a flinch or a acting flustered she simply said "continuing on the page 364, third paragraph", paused as if SHE was looking for her place, and moved on. I assure you, that visitor felt welcomed and encouraged by that little piece of transparency.
Those inserted phrases DO of course interfere with the flow of worship, even when done smoothly. The question then becomes, what is the value that your church places on being welcoming? Is it more or less important than the flow of the service? Is it more or less important than the comfort of the priest, or the comfort of the sacristan, or of one of the lay leaders?
Is radical welcome more or less important than looking like we have it all right, all under control, all put together? Each congregation needs to make the decision as to what is most important themselves. But remember it is people who are feeling unimportant, uncomfortable, and unwelcome, when you decide they are only the second or third most important thing in your parish.