Samtools calmd moves MD field to end of read

I'm ending up with inconsistent field ordering in my BAMs after running calmd to correct an initially-badly-generated MD field. The reads whose MD fields need correcting get corrected, but the MD field is moved to the last column. Here are two adjacent reads from the same BAM; the first one is in its original form, and the second has been modified by calmd.

1618_1392_70    16      chr1    58997   10      50M     *       0       0       AACTCCGGTCCTTCCTATTTATGTTGTTTTTTGTATTCTATGGAGGAATC      *:""4565557;:"%<%)8G4#:OK4""X\H<7S`]K<W`^SET`>0T``      PG:Z:bfast      AS:i:1350       NM:i:2  NH:i:2  IH:i:1  HI:i:1  MD:Z:6A1A41     CS:Z:T1230.0220133220331100002110112300.3212020210302110        CQ:Z:=?;0!>B)37>B,';9B(&-2A..%&<*'%8&)!%.*())%'%'&&%)'* CM:i:6  XA:i:3  XE:Z:--1----------1--4---2-----2------------------4----
1559_1614_1163  0       chr1    59304   255     5M1I1M4I3M4I1M1I30M     *       0       0       AGCAAGTAGAAATGAACTCTAAGCCCCTACACTACACTACAATCATGTGT      5"3J``F4P``P3G`^C3P``N3L\]M3J``N3M``N33P`I33""=""%      PG:Z:bfast      AS:i:300        NM:i:11 NH:i:1  IH:i:1  HI:i:1  CS:Z:T31310213220031201222302300023111231112311032111021        CQ:Z:;'%%<@7&%B=B%%9@5%%BB@%%>5?%%<<@%%?B@%%%B;%%%AA%%% CM:i:4  XA:i:3  XE:Z:-1-------------------------------------------1-02- MD:Z:33T6

Here's the second read, in its original form, before calmd:

1559_1614_1163  0       chr1    59304   255     5M1I1M4I3M4I1M1I30M     *       0       0       AGCAAGTAGAAATGAACTCTAAGCCCCTACACTACACTACAATCATGTGT      5"3J``F4P``P3G`^C3P``N3L\]M3J``N3M``N33P`I33""=""%      PG:Z:bfast      AS:i:300        NM:i:11 NH:i:1  IH:i:1  HI:i:1  MD:Z:5^G1^AGAA3^AACT1^T23T6     CS:Z:T31310213220031201222302300023111231112311032111021        CQ:Z:;'%%<@7&%B=B%%9@5%%BB@%%>5?%%<<@%%?B@%%%B;%%%AA%%% CM:i:4  XA:i:3  XE:Z:-1-------------------------------------------1-02-

I'm not particularly surprised to find optional fields in different orders in different BAMs from different sources; but two different orderings in the same BAM seems like a bit much!

I'm on samtools 0.1.6, and this is SOLiD data mapped by BFAST.

(I've also asked this question on the samtools mailing list, but thought I would help prime the pump over here, as well as giving the formatting tools a bit of a workout. Do people like the read all on one line like that, or is it more annoying to scroll than to read multiline data?)