I'm paranoid about being banned for gardening on a mule, just because I read posts from people saying they were banned.
I have a mule with porcelain pots and maple tables, which I used to garden with. First of all, are you gardening on a mule and not getting banned? What do you think. Is it safe to do that?
Nothing is safe in FFXI anymore
but the chance of being banned for gardening on a character that is not used for/involved in RMT activities is small.
I've been gardening on mules since day one (over 6 years ago) and never had problems. I used to garden for crafting items (such as food ingredients, goldsmithing nuggets/leafs, woodworking beads, ...). Since the ToAU update, I am taking it the easy way (read 'too lazy to spend much time with gardening anymore') and I'm just gardening on 5 mules with 10 pots each using the famous wildgrass recipe. All profits are sold to the nearest NPC except the Gysahl Greens (those I use in a desperate effort to skill up my chocobo digging ability on my main).
So far, I haven't had any problems, warnings or signs of being banned or under investigation for RMT activity.
I do have to say, however, that all of my mules are more or less 'active' characters, in that I did level them all to lvl 20 with a suitable sub at lvl 10 and approprate gear and I use most of them as dedicated crafters (one craft per mule). No naked level 1 WARs without a subjob for me. All of them also have done sufficient quests to obtain hero fame in their home town. Not sure if that is taken into account with the RMT SWAT team to consider a character be banned or not.
Unless you engage in other RMT related activities or are really unfortunate to be picked out by the SWAT's team dubious filters... I think you are safe to garden