Balto-Slavic glottal stop
It is, because o and a merged in Balto-Slavic, and the "glottal stop" became a tonal feature. *mouʔros is a more "conservative" form, reflecting an earlier stage of PBS, but neither the Baltic nor the Slavic languages show any apparent distinction between o and a (the a in Slavic is in fact ā, and reflects a merger of earlier ō and ā, which did not happen in Baltic). Some reconstructions ascribe the merging of a and o to the individual dialects, but that doesn't explain why they merged in all the dialects; it's clearly either a common innovation of Balto-Slavic or a parallel innovation that happened in every Balto-Slavic dialect at the same time. If it's a parallel innovation, it could hardly have happened unless there was still a common dialect area among the various Balto-Slavic dialects, which implies they were still a common language. That in itself is not strange... the West Germanic languages show several parallel innovations that happened after they had become dialectally differentiated from Proto-Germanic.
I moved the entry to Appendix:Proto-Balto-Slavic/mauras.
I added an "alternative reconstructions" section. I don't think any other entries have it yet, but I think it can be useful to make clear that there are different possible ways to interpret it. I haven't turned it into a link because it's just a redirect anyway (as alternative reconstructions usually are, unlike alternative/inflected forms which get entries). Could you add a <ref> to it as well?
Even with the "Alternative reconstructions" section, isn't it still proper to denote the laryngeal with *H and to use *a instead of *o? (In other words, giving the listing under "Alternative reconstructions" as *mauHras)
I like the ===Alternative reconstructions=== header. We should use it for PIE as well.