You're right about the confusing lineage of the 8th Arkansas Infantry. The regiment's original ten companies were consolidated into five companies on April 18, 1862, following the battle of Shiloh. Five new companies were added from a consolidation of the ten companies of the 7th and 9th Arkansas Battalions. Then new company designations were assigned to the consolidated companies.

(new) Co. A was composed of (old) Cos. B and K, 8th Arkansas Infantry.
(new) Co. B was composed of (old) Cos. D and I, 8th Arkansas Infantry.
(new) Co. C was composed of (old) Cos. E and H, 8th Arkansas Infantry.
(new) Co. D was composed of (old) Cos. C and F, 8th Arkansas Infantry.
(new) Co. E was composed of (old) Cos. A and G, 8th Arkansas Infantry.
(new) Co. F was composed of (old) Cos. B and C, 9th Arkansas Battalion.
(new) Co. G was composed of (old) Cos. A and D, 9th Arkansas Battalion.
(new) Co. H was composed of (old) Cos. B and C, 7th Arkansas Battalion.
(new) Co. I was composed of (old) Cos. D and F, 7th Arkansas Battalion.
(new) Co. K was composed of (old) Cos. A and E, 7th Arkansas Battalion.

The Compiled Service Records of the 8th Arkansas Infantry are, for the most part, organized using the (new) company designations.

Arkansas Confederate volunteer companies were normally recruited in a specific locality, composed of residents of that locality. The men normally didn't travel a long ways to enlist. That is why you see so many neighbors and kin serving in the same company together. The place where the company was mustered into service was not necessarily the place where the company was organized. For example, the companies of the 1st Arkansas Mounted Rifles were mustered into service at Fort Smith in June 1861, but they were actually organized and enlisted in a number of counties, such as Independence, Desha, Chicot, Pulaski, Jackson, etc. That's why just slapping a service record against the wall, hoping it will stick, is not always helpful. You have to know where the company was recruited, then you look through the census reports and other records from that county to positively identify a soldier -- especially when you're confronted with two men with similar names.

In the case of Abner Smith, he was a resident of Jackson County, and that's where his company was recruited. He shows up on non-military records in that vicinity. Abner H. Smith was a resident of Van Buren County, and an older man, who just happens to have a coincidentally similar name to the Jackson County man who actually served in the 8th Arkansas.

Anyway, I hope this will help a little. Good luck with your research.