Rehearsal mark at beginning of system should stay within margins
As mentioned at https://musescore.org/en/node/61551#comment-291666.
MuseScore positions certain things relative to the beginnings of measures, which makes sense. But with rehearsal marks, the specific way that MuseScore relates them to barlines leads to the following result if the rehearsal mark is at the beginning of a line:
The volta included in the picture is correctly positioned by default, and could be a model for the positioning of the rehearsal mark.
Here is a manually created example of correct positioning for the rehearsal mark in this circumstance (though the number of staff spaces of horizontal offset depends on the key signature):