In my experience no. I sold roughly 25 images last year, most of which have been online for some time. That said there are some shots I dont upload for that reason, but theres usually something “unique” about them.
Meaning for simple example. A portrait of a fish, is a portrait of a fish. Loosely speaking if youve seen 1 youve seen a million. If an AD is looking for an image of a Brown, I really dont think it matters that you have 30 brown images online and 5 held back.
Also keep in mind some ADs like to peruse your sites, especially once your established with them, when they are looking for something. If your not inlcuding your better images and are only uploading mediochre to good stuff…………………..
So uploading to the web, displaying some on forums, fb etc. I dont its hampered sales for me at all.
A few images I showed here (and a few other forums, that subsequently sold)




double truck

plus quite a few others I dont have online (pdfs of the issue)