Once, a Scrum Master mentioned the “silent card writing, that you use in retros”. I was puzzled, some others too.

There is no rule what you have to do in a retro, which facilitation method you have to use or not use. A good Scrum Master knows a variety of moderation technics, knows how and when to use them, when to alternate, when to repeat the same. 

For the participants, the retrospective should not be boring, but full of creativity and inspiration, a meeting they participate with interest, curiosity, and engagement. This spirit should be inspired by the stage that the Scrum Master sets.

There are good books about retros, describing some (usually 5) steps for facilitating a retro and offering different exercises for those steps.

As with any other meeting, the facilitator’s (i.e. Scrum Master’s) responsibility lies in designing the retro… for the choice of your tools you take into account:
* the team building phase
* the topic of the retro, if given or chosen
* the number of people
* and most of all the variety…

As a retro should never be boring, but full of ideas and creativity, … and so should your input be!