In Novum Testamentum 52 (2010) 267-271, Roy Ciampa (Gordon-Conwell Theological Seminary) has a brief article on the reading of Codex Alexandrinus where the NA27 text has met' allelwn ('with one another'). The textual apparatus in NA27 indicates that Alexandrinus has evidence of the reading met' autou ('with him'). Ciampa points out that in actuality Alexandrinus has no evidence of anything following me. (See the manuscript here at the nttranscripts.uni-muenster.de site.) Most textual critics have assumed that allelwn will not fit on the line and thus autou be a better option. Ciampa contends that meta ths ('with God') should be another option listed among the possible readings of A at 1 John 1:7. These are clearly all options; however, I am not completely convinced that it is impossible for characters of allelwn to fit. The margins are clearly fluid as Ciampa notes, and in the preceding column, it is clear that the scribe is willing to squeeze the characters onto the end of a line. I will have to take a closer look at the manuscript before making a final judgment. This is one of those textual cases where there is not much to go on.
See the reconstruction by Wieland Willker in his comment at Evangelical Textual Criticism. Unfortunately, the reconstruction that he lists does not show the full page. Some of the lines toward the bottom of the page are longer.