I've found that the fabric tends to mend itself when I use a brooch - though I've yet to try a bodkin. It may lend itself to pinning the same portion of fabric each time, rather than making a new hole. I've not pinned a plaid to my jacket or shirt though.

My concern is that it wouldn't hold the plaid in place for long when doing things - I'd guess using a bodkin with tapers and some shape to it would help this, and perhaps it's all in how you pin it (horizontally as opposed to vertically?).

Perhaps there's more reason than not dirtying your Great Kilt in the accounts of highland warriors laying their plaids aside and fighting in their yellow war shirts...