Collaboration in scientific groups can be investigated through analysis of linguistic features associated with politeness strategies. Disagreements, especially, can carry possible threats to colleagues' face. The strategies for redressing these threats can be seen in choices of pronouns or impersonal constructions, and uses of `hedges' — modifications of the force of an assertion. These features indicating politeness overlap with the features used to indicate degrees of doubt or certainty. Thus neither the participants in the collaboration, nor the science studies analyst, can disentangle participants' personal interactions from reasoning, persuasion and decision-making. For instance, the hedging of a criticism out of politeness will be hard to tell from the expression of uncertainty about the evidence or reasoning supporting a suggestion. An exchange of memos in one natural language processing group, concerning a decision over the inclusion of one factor in an algorithm, shows the possible functions of politeness strategies in the course of the group's decision-making.