While I'd be suspicious, I wouldn't necessarily rule a horse out for it without trying it first. My old boy was (he's retired) suitable for novices, depending what they want to do and what sort of novice they were. He never ever bucked, reared or tried to get anyone off, was totally bomproof in traffic etc. For boring hacking and a bit of schooling he'd be great. Anything more exciting and he could get very strong so I rode him on fun rides and beach rides (he didn't jump due to foot problems but when he did, for jumping too) in a waterford gag with two reins. That might look scary to some but he was a pussy cat in it and much happier in it than less harsh bits.
His sharer was very novicey and went through a phase of struggling to hold him (only where he knew he was allowed to canter and he always stopped at the end) so we put him in the gag for her to hack him out for a while until she regained control. Her issue was confidence more than ability though. He'd start walking a bit faster as he knew what was coming, she was anticipating the canter and getting nervous which he interpreted as excitement and "let's go". Once I showed her how I stayed calm but not passive and helped her to do the same, they went back to the snaffle quite happily.
Its the saddle fits that make me twitch! I saw one the other day who was being sold as a companion/ happy hacker because he wouldn't school or jump ... It didn't surprise me with the saddle that was 'fitted' to him, he likely couldn't move properly without being in pain!
The older and wiser i get the less tack i seem to put on my horses!
I did get a lesson that it does not always mean something when I tried to change the bit on one of mine. Previous owners gave me his bit, which I do not know the name for, but it is a gag with 2 fairly narrow mouth pieces, both jointed. I swapped him to a snaffle, which he hated, kept throwing his head around. I have no idea why I did this, but like a complete fool I rushed around having back checked, saddle fitter out before just going back to the original bit. Now I ride him in either a headcollar or the gag, which seems strange, but I have very light hands and he is happy with it. It is not about the strength, he doesn't need a strong bit for control, he somehow just likes it. Someone here told me that these bits are good for horses with fat tongues, so maybe this is it.
My main concern if a novice was to ride him would be that I would not like a strong bit in novice hands, so I suppose actually even though he is polite it would make it difficult to put a novice on him.