In the original manuscript, Oliver Cowdery initially wrote “and I arose and stood”; but then virtually immediately he added the adverbial up (the supralinear insertion was written without any change in the level of ink ﬂow). Variability in the occurrence of up is possible, as is exemplified by the following passage:
In this passage, scribe 2 of 𝓟 omitted the first up, but it was supplied by Oliver Cowdery when he proofed 𝓟 against 𝓞. The 1830 edition has the up, and for this part of the text the 1830 edition was set from 𝓞. So we can be confident that in this instance 𝓞 read “stand up upon their feet”. But later on in the passage, both 𝓟 and the 1830 read “and they arose up and stood upon their feet”, with up after arose and not after stood. Yet the 1906 LDS edition shifted the up from after arose to after stood. This variation argues that in each case we should follow the earliest textual sources. Thus the up will be maintained in Alma 36:8. (For a complete list of cases where Oliver Cowdery either omitted or added up in the text, see under Alma 27:3.)
Summary: Accept in Alma 36:8 the corrected reading in 𝓞 where up follows stood (“and I arose and stood up”).