At that time, and to some extent even today in the British forces, an officer was required to get his Commanding Officer's permission to marry. If he insisted on marrying someone considered unsuitable, he would be told discreetly to move to a less choosy regiment.
According to Gregory Tcherbatoriev(sp?) in Russia, my Native Land the officers of Russian regiments would hold a mess meeting to decide whether the lady concerned could be welcomed into the regiment. I would guess that on most occasions there would be no issue, but, interestingly, the author said that members of the great Moscow merchant families were not considered to be suitable brides for Guards officers because there was a sense that it was not possible to make lots of money in an honourable fashion. Unlike the British Army, however, actresses were acceptable provided they gave up the professional stage before marriage.
Since Leopold Clement was in his 30s, he was senior enough to marry (in the British Army then it was considered improper for any officer below the rank of Captain to marry); the issue was the lady's background.
Ann