Let's begin with a statement from Walter Leaf, Troy, A study in Homeric Geography (1912)
Firstly, as to the "spring of the plain" where the Trojan army is thrice drawn up (x. 160, xi. 56, XX. 3). This I now think Dorpfeld is right in placing at the slightly rising ground on which stand the few huts of Kum Koi, just in the narrow space between the spot where I would place the ford and the modern bridge over the Simois. This is the obvious position for an army defending Troy against an attack from the north : it is well protected on both sides by river beds against flank attacks, and the available front for assault is narrowed to the utmost. The "rise," it is true, is almost microscopic, but it is enough to lift the village above flood water, and Schliemann testifies that it conceals a rider from the view of anyone on the hill of Hissarlik. p 41f
The "microscopic" rise keeps the village of Kum Koi above the floodwaters, he says. I argued the same point in an earlier post. I am not familiar with the remark from Schliemann that Leaf quotes. But it is believable that the hill would conceal a rider from eyes on Hisarlik.
Below is a map provided in another of Leaf's works. He draws the Throsmos precisely where Kum Koi used to sit.
So we know what Leaf thinks of the mound. Now look at two comments from William Gell's The Topography of Troy and its Vicinity, which appeared in 1804.
As the day began to close, we found ourselves at the little village of Koum Kevi; at one extremity of which, after crossing a channel, perhaps that of the brook Thymbrius, we observed a large but not lofty mound, on which were the remains of columns similar to those at Alexandria Troas. p 14
Koum Kevi is of course Kum Koi or Kumkale as it is spelled today. Gell thinks the mound is artificial. He also speculates that it may be the Throsmos, or perhaps the ancient Agora that the invaders allegedly built to go along with their walled camp.The next object worthy of notice js a mount of considerable magnitude on the south of the village of Koum Kevi. There is every reason to suppose it artificial, for it is perfectly insulated, and stands on a dead flat, near the dry channel. The heap is not lofty, and appears to have been levelled, for the purpose of placing on its summit some kind of edifice, of which two or three marble columns are the remains. The building was, probably, a small Ionic temple, but perhaps the columns may have been brought as grave-stones from the ruins of Alexandria Troas or New Ilium. The mount seems too extensive to have been designed for a tumulus, and if it be coeval with the war of Troy, must have been either the Agora of the Greeks, which is mentioned by Homer as the place where the marts and places of worship were erected, or the Throsmos, which was so inconveniently situated for the invaders, while the Trojans were encamped upon it. p 116
Here is Schliemann's 1880 work, Ilios.
Professor Virchow commenced his investigations by digging a number of holes; the first to the right of the bridge which spans the Kalifatli Asmak near Hissarlik. To a depth of 1.25 metres, he found a very compact blackish soil, and below it coarse sand, among which small pieces of quartz, flakes of mica, blackish grains and coarser fragments of rock, were conspicuous. There were no remains of shells. He dug the second hole in the flat dune-like hill on the left bank of the Kalifatli Asmak near Koum Kioi, on which is a Turkish cemetery. He found there to a depth of 2 metres nothing but coarse sand of a dark colour, consisting principally of angular grains of quartz mixed with mica, and some coarser but smoothed pebbles of rock ; no trace of shells. (p88)
Schliemann reports a "flat, dune-like hill on the left bank of the Kalifatli Asmak near Koum Kioi," which is of course Kum Koi or Kumkale.
The existence of this unexplained mound in the plain of Troy is something that scientists working at Troy ought to take seriously.